97. Interleaving String - cocoder39/coco39_LC GitHub Wiki

bool isInterleave(string s1, string s2, string s3) {
        int m = s1.length();
        int n = s2.length();
        if (m + n != s3.length()) {
            return false;
        }
        
        //dp[i][j] = true iff s3[0 .. i + j - 1] is 
        //interleaving of s1[0 .. i - 1] and s2[0 .. j - 1]
        vector<vector<bool>> dp(m + 1, vector<bool>(n + 1));
        dp[0][0] = true;
        for (int i = 1; i <= m; i++) {
            dp[i][0] = dp[i - 1][0] && s1[i - 1] == s3[i - 1];
        }
        for (int j = 1; j <= n; j++) {
            dp[0][j] = dp[0][j - 1] && s2[j - 1] == s3[j - 1];
        }
        
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                dp[i][j] = (dp[i - 1][j] && s1[i - 1] == s3[i + j - 1]) ||
                           (dp[i][j - 1] && s2[j - 1] == s3[i + j - 1]); 
            }
        }
        return dp[m][n];
    }

bool isInterleave(string s1, string s2, string s3) {
        int m = s1.length();
        int n = s2.length();
        if (m + n != s3.length()) {
            return false;
        }
        
        vector<vector<bool>> dp(2, vector<bool>(n + 1));
        dp[0][0] = true;
        for (int j = 1; j <= n; j++) {
            dp[0][j] = dp[0][j - 1] && s2[j - 1] == s3[j - 1];
        }
        
        int pre = 0, cur = 1;
        for (int i = 1; i <= m; i++) {
            dp[cur][0] = dp[pre][0] && s1[i - 1] == s3[i - 1];
            for (int j = 1; j <= n; j++) {
                dp[cur][j] = (dp[pre][j] && s1[i - 1] == s3[i + j - 1]) ||
                             (dp[cur][j - 1] && s2[j - 1] == s3[i + j - 1]);
            }
            swap(pre, cur);
        }
        return dp[pre][n];
    }