LeetCode 0115 - Distinct Subsequences

class Solution {
public:
    int numDistinct(string s, string t) {
        vector<vector<int>> dp(t.size() + 1, vector<int>(s.size() + 1, 0));
        for(int i = 0; i <= s.size(); i++)
            dp[0][i] = 1;
        for(int i = 1; i <= t.size(); i++) {
            for(int j = 1; j <= s.size(); j++) {
                if(t[i-1] == s[j-1])
                    dp[i][j] = dp[i-1][j-1] + dp[i][j-1];
                else
                    dp[i][j] = dp[i][j-1];
            }
        }
        return dp[t.size()][s.size()];
    }
};