2486. Append Characters to String to Make Subsequence

problem

solution

class Solution {
public:
    int appendCharacters(string s, string t) {
        int l =0, r = 0, n =s.size(), m= t.size();
        while(l<n && r<m)
        {
            if(s[l] == t[r]){
                l++;r++;
            }
            else l++;
        }
        return m-r;
    }
};

analysis

• time complexity O(n)
• space complexity O(1)