算法/Algorithm
我个人的力扣答案, #公众号:GeekBro
这是一个持续更新的开源项目
My personal leetcode answers
This is a continually updated open source project
文章/Articles
软件/Softwares
- Anki(https://apps.ankiweb.net/)
- Leetcode-cli(https://github.com/skygragon/leetcode-cli)
书籍/Books
-
《算法技术手册》/ Algorithms in a Nutshell
-
《STL源码剖析》/ The Annotated STL Sources
-
《算法心得：高效算法的奥秘》/ Hacker's Delight, 2nd Edition
-
《数学之美》(A chinese version book by Doctor Wujun)
-
《编程之美 : 微软技术面试心得》(A chinese version book by Mircosoft Developers)
-
Leetcode
-
Math
-
Bit
-
Design
-
Array and String
-
Two Pointers
-
Linked List
-
Binary Search
-
Divide and Conquer
-
Tree Traversal
-
Graph Traversal
-
Backtracking
-
Hash Table
-
Queue
-
Heap
-
Stack
-
Sweep Line
-
Dynamic Programming
-
Red Black Tree
-
Greedy
-
Union Find
-
Trie
-
Other
-
Lintcode
Leetcode
Math
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
| 263.ugly-number |
cpp, python |
O(1) |
O(1) |
Easy |
O(T) = O(LogN), N <= 2^31, O(T) = 32 |
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 002.add-two-numbers |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
|
|
| 007.reverse-integer |
cpp, python |
O(L) |
O(1) |
Easy/S-- |
|
|
| 008.string-to-integer-atoi |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
Overflow Check |
Awesome |
| 009.palindrome-number |
python |
O(N) |
O(1) |
Easy |
|
|
| 012.integer-to-roman |
cpp, python |
O(N) |
Medium |
N = length of results |
|
|
| 013.roman-to-integer |
cpp, python |
O(N) |
Easy |
|
|
|
| 043.multiply-strings |
cpp, python |
O(M*N) |
O(M+N) |
Medium/S++ |
|
|
| 048.rotate-image |
cpp, python |
O(MN) |
O(1) |
Medium/S++ |
|
|
| 067.add-binary |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 202.happy-number |
cpp, python |
O(N) |
Easy |
|
|
|
| 273.integer-to-english-words |
python |
O(N) |
O(N) |
Hard |
|
|
| 311.sparse-matrix-multiplication |
cpp, python |
O(N^3) |
O(N^2) |
Medium/S-- |
|
|
| 326.power-of-three |
python |
O(1) |
O(1) |
Easy/S++ |
|
|
| 342.power-of-four |
python |
O(1) |
O(1) |
Easy/S++ |
|
|
| 415.add-strings |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 829.consecutive-numbers-sum |
python |
O(sqrt(N)) |
O(1) |
Hard |
|
|
| 836.rectangle-overlap |
cpp, python |
O(1) |
O(1) |
Easy |
|
|
Bit
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 136.single-number |
cpp, python |
O(N) |
O(1) |
Easy |
xor |
Perfect |
| 231.power-of-two |
python |
O(1) |
O(1) |
Easy |
|
|
| 318.maximum-product-of-word-lengths |
cpp, python |
O(N^2) |
O(N) |
Medium/S++ |
mask |
Great |
| 393.utf-8-validation |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
|
Perfect |
| 751.ip-to-cidr |
python |
O(N) |
O(1) |
Easy/SSS |
|
|
Design
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 535.encode-and-decode-tinyurl |
python |
O(1) |
O(N) |
Medium |
|
|
Array and String
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
| 038.count-and-say |
python |
N/A |
O(1) |
Easy |
|
| 169.majority-element |
cpp, python |
O(N) |
O(1) |
Easy |
Boyer–Moore majority vote algorithm |
| 229.majority-element-ii |
cpp, python |
O(N) |
O(1) |
Medium |
Boyer–Moore majority vote algorithm |
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 014.longest-common-prefix |
cpp, python |
O(S) |
O(1) |
Easy/S-- |
Trie |
Perfect |
| 031.next-permutation |
cpp, python |
O(N) |
O(1) |
Medium |
Array |
Great |
| 041.first-missing-positive |
python |
O(N) |
O(1) |
Hard |
|
|
| 042.trapping-rain-water |
cpp, python |
O(N) |
O(N) |
Hard |
Scan Twice |
Perfect |
| 054.spiral-matrix |
cpp |
python |
O(N) |
O(1) |
Medium |
|
| 056.merge-intervals |
cpp, python |
O(N * logN) |
O(1) |
Medium |
Sort |
N = number of intervals |
| 057.insert-interval |
cpp, python |
O(N) |
O(1) |
Hard |
Sort |
N = number of intervals |
| 066.plus-one |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 068.text-justification |
python |
O(N) |
O(N) |
Hard |
|
|
| 118.pascals-triangle |
cpp, python |
O(N^2) |
O(1) |
Easy |
|
Perfect |
| 119.pascals-triangle-ii |
cpp, python |
O(N^2) |
O(1) |
Easy |
|
Perfect |
| 157.read-n-characters-given-read4 |
cpp, python |
O(N) |
O(1) |
Easy |
String |
|
| 161.one-edit-distance |
cpp, python |
O(N) |
O(1) |
Medium |
String |
Perfect |
| 163.missing-ranges |
cpp, python |
O(N) |
O(1) |
Medium |
Array |
Mind int overflow |
| 215.kth-largest-element-in-an-array |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
quick-select |
best = O(N), worst = O(N^2) |
| 228.summary-ranges |
python |
O(N) |
O(1) |
Medium |
|
|
| 240.search-a-2d-matrix-ii |
cpp, python |
O(M + N) |
O(1) |
Medium |
|
|
| 251.flatten-2d-vector |
python |
- |
O(N) |
Medium |
|
|
| 271.encode-and-decode-strings |
cpp, python |
O(N) |
O(1) |
Easy |
String |
N = count of chars |
| 277.find-the-celebrity |
cpp, python |
O(N) |
O(1) |
Medium |
|
|
| 280.wiggle-sort |
python |
O(N) |
O(1) |
Medium |
|
|
| 289.game-of-life |
python |
O(MN) |
O(1) |
Medium |
|
|
| $324.wiggle-sort-ii |
python |
O(NLogN) |
O(N) |
Medium |
Follow up |
|
| 370.range-addition |
cpp, python |
O(N + K) |
O(1) |
Medium |
Array |
Perfect |
| 388.longest-absolute-file-path |
cpp, python |
O(N) |
O(N) |
Medium |
String |
|
| 408.valid-word-abbreviation |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 448.find-all-numbers-disappeared-in-an-array |
python |
O(N) |
O(1) |
Easy/SSS |
|
|
| 463.island-perimeter |
python |
O(N) |
O(1) |
Easy/S++ |
|
|
| 527.word-abbreviation |
cpp, python |
O(N * L) |
O(N) |
Hard |
L = avg word length |
|
| 560.subarray-sum-equals-k |
cpp, python |
O(N) |
O(N) |
Medium |
|
Great |
| 657.robot-return-to-origin |
python |
O(N) |
O(1) |
Easy |
|
|
| 674.longest-continuous-increasing-subsequence |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 755.pour-water |
python |
O(N^2) |
O(1) |
Medium/S-- |
|
|
| 796.rotate-string |
cpp, python |
O(N) |
O(1) |
Easy |
string |
|
| 929.unique-email-addresses |
python |
O(N) |
O(N) |
Easy |
|
|
| Problem |
Solution |
Time |
Difficulty |
Tag |
Note |
| 350.intersection-of-two-arrays-ii |
python |
O(N * logN) |
Easy |
|
|
| 485.max-consecutive-ones |
cpp |
O(N) |
Easy |
|
|
| 498.diagonal-traverse |
cpp |
O(MN) |
Medium |
|
|
| 561.array-partition-i |
cpp |
O(N * logN) |
Easy |
|
|
| 724.find-pivot-index |
cpp |
O(N) |
Easy |
|
|
| 747.largest-number-at-least-twice-of-others |
cpp |
O(N) |
Easy |
|
|
| 832.flipping-an-image |
python |
O(N) |
O(N) |
Easy |
|
| 859.buddy-strings |
cpp |
O(N) |
Easy |
string |
|
Two Pointers
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 003.longest-substring-without-repeating-characters |
cpp, python |
O(N) |
O(N) |
Medium |
|
|
| 011.container-with-most-water |
python |
O(N) |
O(1) |
Medium |
|
|
| 015.3sum |
cpp, python |
O(N^2) |
O(1) |
Medium/S++ |
|
Awesome |
| 016.3sum-closest |
cpp, python |
O(N^2) |
O(1) |
Medium |
|
Cool |
| 018.4sum |
cpp, python |
O(N^3) |
O(1) |
Medium |
|
Awesome |
| 019.remove-nth-node-from-end-of-list |
cpp, python |
O(N) |
O(1) |
Medium |
|
Perfect |
| 026.remove-duplicates-from-sorted-array |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 027.remove-element |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 028.implement-strstr |
cpp, python |
O(M + N) |
O(1) |
Easy |
Pattern Searching |
KMP |
| 042.trapping-rain-water |
cpp, python |
O(N) |
O(1) |
Hard |
Two Pointers |
|
| 075.sort-colors |
cpp python |
O(N) |
O(1) |
Medium |
counting-sort |
|
| 076.minimum-window-substring |
cpp, python |
O(N) |
O(N) |
Hard |
|
|
| 088.merge-sorted-array |
cpp, python |
O(N + M) |
O(1) |
Easy |
|
Perfect |
| 125.valid-palindrome |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 159.longest-substring-with-at-most-two-distinct-characters |
cpp, python |
O(N) |
O(N) |
Hard |
|
|
| 167.two-sum-ii-input-array-is-sorted |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 209.minimum-size-subarray-sum |
cpp, python |
O(N) |
O(1) |
Medium |
|
|
| 234.palindrome-linked-list |
cpp, python |
O(N) |
O(1) |
Easy |
|
maybe Harder |
| 283.move-zeroes |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 340.longest-substring-with-at-most-k-distinct-characters |
cpp, python |
O(N) |
O(N) |
Hard |
|
Cool |
| 344.reverse-string |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 345.reverse-vowels-of-a-string |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 350.intersection-of-two-arrays-ii |
cpp, python |
O(K * logK), k = max(M, N) |
O(1) |
Easy |
hash, binary-search |
|
| 532.k-diff-pairs-in-an-array |
cpp, python |
O(N * logN) |
O(1) |
Easy |
Hash |
|
| 844.backspace-string-compare |
cpp, python |
O(N) |
O(1) |
Easy |
stack |
|
Linked List
There is actually no algorithm in linked list question, but is really tricky to get one right
| Problem |
Solution |
Time |
Space |
Difficulty |
Grade |
Note |
| 021.merge-two-sorted-lists |
cpp, python |
O(N) |
O(1) |
Easy |
Perfect |
|
| 024.swap-nodes-in-pairs |
cpp, python |
O(N) |
O(1) |
Medium |
Great |
|
| 025.reverse-nodes-in-k-group |
cpp, python |
O(N) |
O(1) |
Hard/S-- |
Perfect |
|
| 086.partition-list |
cpp, python |
O(N) |
O(1) |
Medium |
Perfect |
|
| 092.reverse-linked-list-ii |
cpp, python |
O(N) |
O(1) |
Medium |
Perfect |
|
| 141.linked-list-cycle |
cpp, python |
O(N) |
O(1) |
Easy |
perfect |
|
| 142.linked-list-cycle-ii |
cpp, python |
O(N) |
O(1) |
Medium/S++ |
Perfect |
|
| 160.intersection-of-two-linked-lists |
cpp, python |
O(N + M) |
Easy |
Perfect |
two-pointers |
|
| 206.reverse-linked-list |
cpp, python |
O(N) |
O(1) |
Easy/S++ |
Perfect |
|
| Problem |
Solution |
Time |
Difficulty |
Tag |
Note |
| 61.rotate-list |
python |
O(N) |
Medium |
|
|
| 143.reorder-list |
python |
O(N) |
Medium |
|
|
| 138.copy-list-with-random-pointer |
python |
O(N) |
Medium |
|
|
| 148.sort-list |
python |
O(N * logN) |
Medium |
|
|
| 203.remove-linked-list-elements |
python |
O(N) |
Easy |
|
|
| 237.delete-node-in-a-linked-list |
python |
O(1) |
Easy |
|
|
| 328.odd-even-linked-list |
python |
O(N) |
Medium |
|
|
Binary Search
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
| 004.median-of-two-sorted-arrays |
cpp, python |
O(log(N)) |
O(1) |
|
TODO: find kth solution |
| 278.first-bad-version |
cpp, python |
O(logN) |
O(1) |
Easy |
3 template |
| 658.find-k-closest-elements |
cpp, python |
Log(N - K) |
O(1) |
Medium |
|
| 704.binary-search |
cpp, python |
O(logN) |
O(1) |
Easy |
TODO: missing one template |
| 1150.check-if-a-number-is-majority-element-in-a-sorted-array.cpp |
cpp, python |
O(logN) |
O(1) |
Easy |
|
| Problem |
Solution |
Time |
Space |
Difficulty |
Statistic |
Note |
| 029.divide-two-integers |
cpp, python |
O(logN) |
O(1) |
Medium/S++ |
Math |
|
| $033.search-in-rotated-sorted-array |
cpp, python |
O(logN) |
O(1) |
Medium/S++ |
|
Perfect |
| 034.find-first-and-last-position-of-element-in-sorted-array |
cpp, python |
O(LogN) |
O(1) |
Medium |
|
Perfect |
| 050.powx-n |
cpp, python |
O(logN) |
O(1) |
Medium/S++ |
|
|
| $069.sqrtx |
cpp, python |
O(logN) |
O(1) |
Easy |
|
Perfect |
| 074.search-a-2d-matrix |
cpp, python |
O(logN) |
O(1) |
Medium |
N = row * col |
|
| 081.search-in-rotated-sorted-array-ii |
cpp, python |
O(logN) ~ O(N) |
O(1) |
Medium/S++ |
|
|
| 153.find-minimum-in-rotated-sorted-array |
cpp, python |
O(logN) |
O(1) |
Medium |
|
Perfect |
| 154.find-minimum-in-rotated-sorted-array-ii |
cpp, python |
O(logN) ~ O(N) |
O(1) |
Hard |
|
|
| 162.find-peak-element |
cpp, python |
O(logN) |
O(1) |
Medium |
|
Perfect |
| 270.closest-binary-search-tree-value |
cpp, python |
O(LogN) |
O(1) |
Easy |
|
Perfect |
| 302.smallest-rectangle-enclosing-black-pixels |
cpp, python |
O(MLogN + NLogM) |
O(1) |
Hard/SSS |
|
Perfect |
| 367.valid-perfect-square |
cpp, python |
O(LogN) |
O(1) |
Easy |
|
Perfect |
| 374.guess-number-higher-or-lower |
cpp, python |
O(LogN) |
O(1) |
Easy |
|
Perfect |
| 702.search-in-a-sorted-array-of-unknown-size |
cpp, python |
O(LogN) |
O(1) |
Medium |
|
Perfect |
| 852.peak-index-in-a-mountain-array |
cpp, python |
O(logN) |
O(1) |
Easy |
Golden-section search |
|
| 1150.check-if-a-number-is-majority-element-in-a-sorted-array.cpp |
cpp, python |
O(logN) |
O(1) |
Easy |
|
|
Divide and Conquer
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
| 098.validate-binary-search-tree |
cpp, python |
O(N) |
O(1) |
Medium |
|
| 236.lowest-common-ancestor-of-a-binary-tree |
cpp, python |
O(N) |
O(1) |
Medium |
|
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 104.maximum-depth-of-binary-tree |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 110.balanced-binary-tree |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 273.integer-to-english-words |
python |
O(N) |
O(N) |
Hard |
|
|
| 282.expression-add-operators |
cpp, python |
O(2 ^ N) |
O(N) |
Hard/SSS |
DFS |
N = length of input |
| 687.longest-univalue-path |
cpp, python |
O(N) |
O(1) |
Easy/S++ |
|
Perfect |
Tree Traversal
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 94.binary-tree-inorder-traversal |
cpp, python |
O(N) |
O(1) |
Medium/S++ |
|
Perfect |
| 102.binary-tree-level-order-traversal |
cpp, python |
O(N) |
O(H) |
Medium |
|
Perfect |
| 103.binary-tree-zigzag-level-order-traversal |
cpp, python |
O(N) |
O(N) |
Medium |
|
Perfect |
| 107.binary-tree-level-order-traversal-ii |
cpp, python |
O(N) |
O(N) |
Easy |
|
Perfect |
| 114.flatten-binary-tree-to-linked-list |
cpp, python |
O(N) |
O(1) |
Medium |
|
Cool |
| 130.surrounded-regions |
cpp, python |
O(MN) |
O(M & N) |
Medium |
BFS |
|
| 144.binary-tree-preorder-traversal |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
|
Perfect |
| 145.binary-tree-postorder-traversal |
cpp, python |
O(N) |
O(1) |
Hard/SSS |
|
Perfect |
| 156.binary-tree-upside-down |
cpp, python |
O(V) |
O(1) |
Medium |
|
|
| 173.binary-search-tree-iterator |
cpp, python |
O(1) |
O(H) |
Medium/S-- |
|
Perfect |
| 257.binary-tree-paths |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 285.inorder-successor-in-bst |
cpp, python |
O(H) |
O(1) |
Medium |
BST |
H = height of the tree |
| 286.walls-and-gates |
cpp, python |
O(MN) |
O(MN) |
Medium |
BFS |
|
| 297.serialize-and-deserialize-binary-tree |
cpp, python |
O(N) |
O(N) |
Hard |
|
Cool |
| 314.binary-tree-vertical-order-traversal |
cpp, python |
O(V) |
O(V) |
Medium |
|
|
| 366.find-leaves-of-binary-tree |
cpp, python |
O(V) |
O(V) |
Medium |
|
|
| 426.convert-binary-search-tree-to-sorted-doubly-linked-list |
cpp, python |
O(N) |
O(1) |
Medium |
|
Perfect |
| 538.convert-bst-to-greater-tree |
cpp, python |
O(V) |
O(1) |
Easy |
|
|
Graph Traversal
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 127.word-ladder |
cpp, python |
O(N^2 * L^2) |
O(N) |
Medium/S++ |
BFS |
Bad |
| 133.clone-graph |
cpp, python |
O(V + E) |
O(N) |
Medium |
|
Great |
| 200.number-of-islands |
cpp, python |
O(MN) |
O(MN) |
Medium |
BFS/DFS |
union-find |
| 207.course-schedule |
cpp, python |
O(V + E) |
O(V + E) |
Medium |
|
Perfect |
| 210.course-schedule-ii |
cpp, python |
O(V + E) |
O(V) |
Medium |
topological-sort |
Awesome |
| 269.alien-dictionary |
python |
O(V + E) |
O(V + E) |
Hard |
|
|
| 323.number-of-connected-components-in-an-undirected-graph |
cpp, python |
O(V+E) |
O(V+E) |
Medium |
union-find |
Bad |
| 433.minimum-genetic-mutation |
cpp, python |
O(V + E) |
O(N) |
Medium |
|
|
| 444.sequence-reconstruction |
cpp, python |
O(V+E) |
O(V) |
Medium |
topological-sort |
|
| 773.sliding-puzzle |
python |
O(V + E) |
O(N) |
Hard/SSS |
|
|
| 815.bus-routes |
python |
O(V + E) |
O(N) |
Hard/SSS |
|
|
Backtracking
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
| 037.sudoku-solver |
python |
O(2 ^ N) |
O(N) |
Medium |
N = black count |
| Problem |
Solution |
Time |
Space |
Difficulty |
Tag |
Note |
| 017.letter-combinations-of-a-phone-number |
cpp, python |
O(2 ^ N) |
O(N) |
Medium |
|
|
| 022.generate-parentheses |
python |
O(ans) |
O(N) |
Medium |
|
|
| 039.combination-sum |
cpp, python |
O(N^K), k=target/min |
O(K) |
Medium |
DFS |
Perfect |
| 040.combination-sum-ii |
cpp, python |
O(2^K), k=target/min |
O(K) |
Medium/S-- |
DFS |
Perfect |
| 046.permutations |
cpp, python |
O(N * N!) |
O(N) |
Medium |
DFS |
Perfect |
| 047.permutations-ii |
cpp, python |
O(N * N!) |
O(N) |
Medium/S++ |
DFS |
Perfect |
| 051.n-queens |
cpp, python |
O(N^N) |
O(N) |
Hard |
DFS |
Awesome |
| 052.n-queens-ii |
cpp, python |
O(N^N) |
O(N) |
Hard |
DFS |
Perfect |
| 078.subsets |
cpp, python |
O(N * 2^N) |
O(N) |
Medium |
DFS/Iteration/Bit |
|
| 079.word-search |
cpp, python |
O(MN * L^2), L = length of words |
O(MN) |
Medium |
DFS |
|
| 090.subsets-ii |
cpp, python |
O(N * 2^N) |
O(N) |
Medium(S++) |
DFS/Iteration |
|
| 126.word-ladder-ii |
cpp, python |
- |
O(N) |
Hard/SSS |
DFS Pruning |
Awesome |
| 131.palindrome-partitioning |
cpp, python |
O(2^N) |
O(N) |
Medium |
DFS |
Perfect |
Hash Table
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
| 036.valid-sudoku |
cpp, python |
O(N ^ 2) |
O(N ^ 2) |
Medium |
array-indexes |
| Problem |
Solution |
Time |
Space |
Difficulty |
Grade |
Note |
| 001.two-sum |
cpp, python |
O(N) |
O(N) |
Easy |
|
Perfect |
| 030.substring-with-concatenation-of-all-words |
cpp, python |
O(MN) |
O(M) |
Hard/SSS |
Cool |
TODO O(N) |
| 49.group-anagrams |
cpp |
O(N * k * Logk) |
Medium |
|
|
|
| 170.two-sum-iii-data-structure-design |
cpp, python |
O(N) |
O(N) |
Easy |
Awesome |
|
| 202.happy-number |
cpp, python |
O(N) |
Easy |
|
|
|
| 217.contains-duplicate |
cpp |
O(N) |
Easy |
|
|
|
| 219.contains-duplicate-ii |
cpp |
O(N) |
Easy |
|
|
|
| 242.valid-anagram |
cpp, python |
O(N) |
O(1) |
Easy |
Perfect |
|
| 249.group-shifted-strings |
cpp |
O(N * K) |
Medium |
|
|
|
| 347.top-k-frequent-elements |
cpp |
O(N * LogN) |
Medium |
|
|
TODO: quick-sort, bucket-sort |
| 350.intersection-of-two-arrays-ii |
cpp |
O(MN) |
Easy |
|
|
|
| 359.logger-rate-limiter |
cpp |
O(1) |
Easy |
|
|
amortized |
| 380.insert-delete-getrandom-o1 |
cpp |
O(1) |
Medium |
|
|
|
| 447.number-of-boomerangs |
cpp, python |
O(N^2) |
O(N) |
Easy |
Cool |
|
| 454.4sum-ii |
cpp |
O(N ^ 2) |
Medium |
|
|
|
| 599.minimum-index-sum-of-two-lists |
cpp |
O(M + N) |
Easy |
|
|
|
| 652.find-duplicate-subtrees |
cpp |
O(N) |
Medium |
|
|
|
| 760.find-anagram-mappings |
python |
O(N) |
O(N) |
Easy |
|
|
| 771.jewels-and-stones |
cpp |
O(M + N) |
Easy |
|
|
|
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 128.longest-consecutive-sequence |
cpp, python |
O(N) |
O(N) |
Hard/S++ |
Union-find |
|
| 205.isomorphic-strings |
cpp, python |
O(N) |
O(N) |
Easy |
|
|
| 246.strobogrammatic-number |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| 288.unique-word-abbreviation |
cpp, python |
O(1) |
O(N) |
Medium |
|
|
| 349.intersection-of-two-arrays |
cpp, python |
O(K * logK), k = max(M, N) |
O(1) |
Easy |
two-pointers, binary-search |
perfect |
| 387.first-unique-character-in-a-string |
cpp, python |
O(N) |
O(N) |
Easy |
|
|
| 438.find-all-anagrams-in-a-string |
cpp, python |
O(N) |
O(N) |
Easy |
|
|
queue
| Problem |
Solution |
Time |
Space |
Difficulty |
Grade |
Node |
| 239.sliding-window-maximum |
cpp, python |
O(N) |
O(N) |
Hard |
Great |
|
| 346.moving-average-from-data-stream |
cpp, python |
O(1) |
O(N) |
Easy |
Perfect |
|
| 933.number-of-recent-calls |
cpp, python |
O(Inputs) |
O(1) |
Easy |
Perfect |
Fast I/O for Competitive Programming |
Heap
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| $023.merge-k-sorted-lists |
cpp, python |
O(N * LogK) |
O(K) |
Hard |
|
Perfect |
| 295.find-median-from-data-stream |
cpp, python |
O(NLogN) |
O(N) |
Medium |
|
Cool |
| 378.kth-smallest-element-in-a-sorted-matrix |
cpp, python |
O((K + M) * LogM) |
O(M) |
Medium |
TODO: binary-search, O(N) solution |
|
| 407.trapping-rain-water-ii |
cpp, python |
O(M * N * Log(M + N)) |
O(M + N) |
Hard/SSS |
|
Bad |
Stack
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 020.valid-parentheses |
cpp, python |
O(N) |
O(N) |
Easy |
|
Perfect |
| 084.largest-rectangle-in-histogram |
cpp, python |
O(N) |
O(N) |
Hard/S++ |
|
Perfect |
| 085.maximal-rectangle |
cpp, python |
O(MN) |
O(N) |
Hard/SSS |
|
Perfect |
| 155.min-stack |
cpp, python |
O(1) |
O(N) |
Easy/S-- |
|
Cool |
| 341.flatten-nested-list-iterator |
python |
- |
O(N) |
Medium/S++ |
|
|
| 394.decode-string |
cpp, python |
O(N) |
O(N) |
Medium |
|
Perfect |
| 654.maximum-binary-tree |
cpp, python |
O(N) |
O(N) |
Hard/SSS |
|
Perfect |
| 739.daily-temperatures |
python |
O(N) |
O(N) |
Medium |
|
|
Sweep Line
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| $253.meeting-rooms-ii |
cpp, python |
O(NlogN) |
O(N) |
Medium |
|
Perfect |
Dynamic Programming
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 005.longest-palindromic-substring |
python |
O(N^2) |
O(1) |
Medium |
|
|
| 010.regular-expression-matching |
cpp, python |
O(MN) |
O(MN) |
Hard/S++ |
Sequence |
|
| 044.wildcard-matching |
cpp, python |
O(MN) |
O(MN) |
Hard |
Sequence |
|
| 053.maximum-subarray |
cpp, python |
O(N) |
O(1) |
Easy |
|
Perfect |
| 062.unique-paths |
cpp, python |
O(MN) |
O(MN) |
Medium |
Coordinates |
|
| 063.unique-paths-ii |
cpp, python |
O(MN) |
O(MN) |
Medium |
Coordinates |
|
| 064.minimum-path-sum |
cpp, python |
O(MN) |
O(MN) |
Medium |
Coordinates |
|
| 070.climbing-stairs |
cpp, python |
O(N) |
O(1) |
Easy |
Coordinates |
Perfect |
| 072.edit-distance |
cpp, python |
O(MN) |
O(N) |
Hard/S-- |
Sequence |
|
| 087.scramble-string |
cpp, python |
O(N^4) |
O(N^3) |
Hard/SSS |
Range |
|
| 091.decode-ways |
cpp, python |
O(N) |
O(N) |
Medium/S++ |
Partition |
|
| 097.interleaving-string |
cpp, python |
O(MN) |
O(MN) |
Hard/S-- |
Sequence |
|
| 115.distinct-subsequences |
cpp, python |
O(MN) |
O(MN) |
Hard/S-- |
Sequence |
|
| 120.triangle |
cpp, python |
O(N^2) |
O(N) |
Medium |
Coordinates |
Perfect |
| 132.palindrome-partitioning-ii |
cpp, python |
O(N^2) |
O(N^2) |
Hard |
Partition |
|
| 188.best-time-to-buy-and-sell-stock-iv |
cpp, python |
O(N*K) |
O(N * K) |
Hard/SSS |
|
|
| 198.house-robber |
cpp, python |
O(N) |
O(1) |
Easy |
Sequence |
Perfect |
| 121.best-time-to-buy-and-sell-stock |
cpp, python |
O(N) |
O(1) |
Easy |
Coordinates |
|
| 123.best-time-to-buy-and-sell-stock-iii |
cpp, python |
O(N) |
O(N) |
Hard/SSS |
|
|
| 213.house-robber-ii |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
Sequence |
Perfect |
| 221.maximal-square |
cpp, python |
O(MN) |
O(N) |
Medium/S-- |
Coordinates |
Perfect |
| 256.paint-house |
cpp, python |
O(N) |
O(N) |
Easy/S-- |
Sequence |
|
| 265.paint-house-ii |
cpp, python |
O(MN) |
O(MN) |
Hard |
Sequence |
|
| 276.paint-fence |
cpp, python |
O(N) |
O(1) |
Easy/SSS |
|
Perfect |
| 279.perfect-squares |
cpp, python |
O(N ^ 1.5) |
O(N) |
Medium |
Partition |
|
| 300.longest-increasing-subsequence |
cpp, python |
O(NlogN) |
O(N) |
Medium/SSS |
Binary-search / DP |
Perfect |
| 312.burst-balloons |
cpp, python |
O(N^3) |
O(N^2) |
Hard/S-- |
Range |
|
| 322.coin-change |
cpp, python |
O(L*N) |
O(N) |
Medium |
N = amount, L = len(coins) |
|
| 338.counting-bits |
cpp, python |
O(N) |
O(1) |
Medium/S-- |
Bit-manipulation |
|
| 354.russian-doll-envelopes |
cpp, python |
O(N*logN) |
O(N) |
Hard/S-- |
Coordinates |
|
| $361.bomb-enemy |
cpp, python |
O(MN) |
O(MN) |
Medium/S++ |
Coordinates |
|
| $368.largest-divisible-subset |
cpp, python |
O(N^2) |
O(N) |
Medium/S++ |
Coordinates |
Awesome |
| 377.combination-sum-iv |
cpp, python |
O(M*N) |
O(N) |
Medium |
Backpack |
|
| 474.ones-and-zeroes |
cpp, python |
O(LMN) |
O(LMN) |
Medium |
Sequence |
|
| 516.longest-palindromic-subsequence |
cpp, python |
O(N^2) |
O(N^2) |
Medium |
|
|
| 787.cheapest-flights-within-k-stops |
python |
O(K * E) |
O(N) |
Hard/SSS |
|
|
Red Black Tree
Since python got no built-in AVL data-structure, these questions written in python may perform worse
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| $683.k-empty-slots |
cpp, python |
O(NLogN) |
O(N) |
Hard/SSS |
Min Queue |
Bad |
Greedy
| Problem |
Solution |
Time |
Space |
Difficulty |
Tag |
Note |
| 45.jump-game-ii |
cpp, python |
O(N) |
O(1) |
Hard |
|
|
| 055.jump-game |
cpp, python |
O(N) |
O(1) |
Medium |
dynamic-programming |
|
| 122.best-time-to-buy-and-sell-stock-ii |
cpp, python |
O(N) |
O(1) |
Easy |
|
|
| $406.queue-reconstruction-by-height |
cpp, python |
O(N^2) |
O(1) |
Medium/S++ |
Sort Multiple Keys |
|
Union Find
| Problem |
Solution |
Time |
Space |
Difficulty |
Note |
Grade |
| 261.graph-valid-tree |
cpp, python |
O(E) |
O(N) |
Medium |
BFS/DFS |
Perfect |
| 305.number-of-islands-ii |
cpp, python |
O(N) |
O(MN) |
Hard |
|
N = len(positions) |
| 721.accounts-merge |
cpp, python |
O(MN) |
O(MN) |
Medium |
|
|
| 924.minimize-malware-spread |
python |
O(N^2) |
O(N) |
Hard |
TODO |
Bad |
Trie
| Problem |
Solution |
Time |
Space |
Difficulty |
Tag |
Note |
| 208.implement-trie-prefix-tree |
cpp, python |
O(L) |
O(N * L) |
Medium |
- |
L = len(word), N = number of words |
| 211.add-and-search-word-data-structure-design |
cpp, python |
add = O(L), find >= O(L) |
O(N * L) |
Medium/S-- |
DFS |
L = len(word), N = count(words) |
| 212.word-search-ii |
cpp, python |
O(M * N * L * L) |
MAX(O(MN), O(K * L)) |
Hard |
DFS |
K = number of words, L = avg length of words |
| 336.palindrome-pairs |
python |
O(N * L^2) |
O(N) |
Hard/SSS |
|
|
| 425.word-squares |
cpp, python |
O(-) |
O(NL) |
Hard/SSS |
DFS Pruning |
|
| 677.map-sum-pairs |
cpp, python |
O(L), O(KL) |
O(N * L) |
Medium |
|
L = length of input, k = number of items found |
Other
| Problem |
Solution |
Difficulty |
Tag |
Note |
| 175.combine-two-tables |
sql |
Easy |
SQL |
|
Lintcode
Below are Lintcode questions that worth trying
| Problem |
Solution |
Time |
Space |
Difficulty |
Tag |
Note |
| 039.recover-rotated-sorted-array |
cpp, python |
O(N) |
O(1) |
Easy/S++ |
Binary-search, Two-pointers |
|
| 077.longest-common-subsequence |
cpp, python |
O(M*N) |
O(M*N) |
Medium |
dynamic-programming |
|
| 081.find-median-from-data-stream |
cpp, python |
O(N * LogN) |
O(N) |
Hard |
Heap |
|
| 089.k-sum |
cpp, python |
O(NKT) |
O(NKT) |
Hard |
dynamic-programming |
|
| 091.minimum-adjustment-cost |
cpp, python |
O((100^2)N) |
O(100N) |
Medium |
dynamic-programming |
|
| 092.backpack |
cpp, python |
O(M*N) |
O(M) |
Medium |
dynamic-programming |
|
| 125.backpack-ii |
cpp, python |
O(M*N) |
O(M) |
Medium/S++ |
dynamic-programming |
|
| 139.subarray-sum-closest |
cpp, python |
O(NlogN) |
O(N) |
Medium |
Subarray |
|
| 144.interleaving-positive-and-negative-numbers |
cpp, python |
O(N) |
O(1) |
Medium |
two-pointers |
|
| 183.wood-cut |
cpp, python |
O(N * LogN) |
O(1) |
Medium/S-- |
binary-search |
|
| 382.triangle-count |
cpp, python |
O(N^2) |
O(1) |
Medium |
two-pointers |
|
| 390.find-peak-element-ii |
cpp, python |
O(M + N) |
O(1) |
Hard/SSS |
binary-search |
|
| 391.number-of-airplanes-in-the-sky |
cpp, python |
O(NlogN) |
O(N) |
Medium |
sweep-line |
|
| 394.coins-in-a-line |
cpp, python |
O(N) |
O(N) |
Medium |
dynamic-programming |
|
| 396.coins-in-a-line-iii |
cpp, python |
O(N^2) |
O(N^2) |
Hard/SSS |
dynamic-programming |
|
| 437.copy-books |
cpp, python |
O(K * N^2) / O(N * LogA) |
O(NK) |
Hard/SSS |
dynamic-programming / binary-search |
|
| 440.backpack-iii |
cpp, python |
O(MN) |
O(M) |
Hard/SSS |
dynamic-programming |
|
| 447.search-in-a-big-sorted-array |
cpp, python |
O(LogK) |
O(1) |
binary-search |
Medium/S++ |
|
| 465.kth-smallest-sum-in-two-sorted-arrays |
cpp, python |
O((K + N) * LogN) |
O(N) |
Hard |
heap |
N = B.size() |
| 543.kth-largest-in-n-arrays |
cpp, python |
O(M * N * LogK) |
O(K) |
Easy |
heap |
|
| 526.load-balancer |
cpp, python |
O(1) |
O(N) |
Medium |
Hash + Array |
|
| 563.backpack-v |
cpp, python |
O(M*N) |
O(M) |
Medium |
dynamic-programming |
|
| 586.sqrtx-ii |
cpp, python |
O(logN) |
O(N) |
Medium |
binary-search |
|
| 589.connecting-graph |
cpp, python |
O(1) |
O(N) |
Medium |
union-find |
|
| 590.connecting-graph-ii |
cpp, python |
O(1) |
O(N) |
Medium |
union-find |
|
| 591.connecting-graph-iii |
cpp, python |
O(1) |
O(N) |
Medium |
union-find |
|
| 598.zombie-in-matrix |
cpp, python |
O(MN) |
O(MN) |
Medium |
graph-traversal |
|
| 611.knight-shortest-path |
cpp, python |
O(MN) |
O(MN) |
Medium |
graph-traversal |
|
| 618.search-graph-nodes |
cpp, python |
O(V + E) |
O(V) |
Medium |
tree-traversal |
|
| 629.minimum-spanning-tree |
cpp, python |
O(N * logN) |
O(N) |
Hard |
union-find |
Prim, Kruskal |
| 652.factorization |
cpp, python |
O(N) |
O(LogN) |
Medium/S++ |
N = input number |
|
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