97. 交错字符串(LeetCode)(DP)

97. 交错字符串

class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        int n = s1.size(), m = s2.size();
        if(s3.size() != n + m) return false;

        vector<vector<bool>> f(n + 1, vector<bool>(m + 1, 0));

        s1 = " " + s1, s2 = " " + s2; s3 = " " + s3;
        for(int i = 0; i <= n; ++i){
            for(int j = 0; j <= m; ++j){
                if(!i && !j) f[i][j] = true;
                else{
                    if(i && s1[i] == s3[i+j]) f[i][j] = f[i-1][j];
                    if(j && s2[j] == s3[i+j]) f[i][j] = f[i][j] | f[i][j-1]; 
                }
            }
        }

        return f[n][m];
    }
};