### PROBLEM LINK:

**Editorialist:** Karan Aggarwal

### DIFFICULTY:

CAKEWALK

### PREREQUISITES:

Strings

### PROBLEM:

Given 2 string **L** and **K** of length **N** and **N-1** respectively, tell whether **K** can be formed by removing exactly 1 character from **L**.

### EXPLANATION:

This problem can be reduced to a more general problem of given 2 string, find whether one is a sub-sequence of other.

This can be done in O(N) by keeping a track of how much of the smaller string **K** has been seen till now in the bigger string **L**.

Let **seen** represent the length **K** seen in *L[0…i-1]*

`seen = 0; for(int i=0; i< N; i++) if(K[seen] == L[i]) seen = seen+1`

If **seen** == N-1 in the loop, then we string **K** is a sub-sequence of string **L** .

**Complexity** : **O(N)**