Add Linear Search Algorithm

[binnn228]

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[mohitchakraverty]

I would like to help :-)

[drashan14]

Mam Could i do this task.

[yashpaddalwar]

Please assign this task to me

[williamfiset]

We don't need this algorithm, it's trivial to implement with just a for loop:

int key = ...;
for (int i = 0; i < n; i++)
  if (array[i] == key)
    return i;