Append Characters to String to Make Subsequence.cpp

class Solution {
public:
    int appendCharacters(string s, string t) {
        int s_index = 0, t_index = 0;
        int s_length = s.length(), t_length = t.length();
    
        while (s_index < s_length && t_index < t_length) {
            if (s[s_index] == t[t_index]) {
                t_index++;
            }
            s_index++;
        }
    
        return t_length - t_index;
    }
};