class Solution {public:    bool isInterleave(string s1, string s2, string s3) {        int l1 = s1.length();        int l2 = s2.length();        int l3 = s3.length();                if(l3 != (l1+l2))            return false;                bool dp[l1+1][l2+1];        for(int i=0;i<l1+1;i++){            for(int j=0;j<l2+1;j++){                if(i==0 && j==0){                    dp[i][j] = true;                }else if (i == 0){                    dp[i][j] = (dp[i][j-1] && s2[j-1] == s3[i+j-1]);                }else if (j == 0){                    dp[i][j] = (dp[i-1][j] && s1[i-1] == s3[i+j-1]);                }else {                    dp[i][j] = (dp[i][j-1] && s2[j-1] == s3[i+j-1]) || (dp[i-1][j] && s1[i-1] == s3[i+j-1]);                 }            }        }        return dp[l1][l2];    }};