Append Characters to String to Make Subsequence.cpp

class Solution {
public:
    int appendCharacters(string s, string t) {
        int i=0;
        int j=0;

        while(i<s.length() && j<t.length()){
            if(s[i]==t[j]) i++,j++;
            else i++;
        }
        return t.length()-j;

    }
};