LeetCode-Interleaving String

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.

For example,
Given:
s1 = "aabcc",
s2 = "dbbca",

When s3 = "aadbbcbcac", return true.
When s3 = "aadbbbaccc", return false.

动态规划，前i个s1和前j个s2能否组成前i+j

class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        // Note: The Solution object is instantiated only once and is reused by each test case.    
        if(s1.length()+s2.length()!=s3.length()){
            return false;
        }
        vector<vector<bool> > m;
        vector<bool> one;
        one.resize(s2.length()+1,false);
        m.resize(s1.length()+1,one);
        m[0][0]=true;
        bool flag=true;
        for(int i=1;i<=s1.length();i++){
            if(s1[i-1]==s3[i-1]){
                if(flag)m[i][0]=true;
            }
            else{
                flag=false;
            }
        }
        flag=true;
        for(int i=1;i<=s2.length();i++){
            if(s2[i-1]==s3[i-1]){
                if(flag)m[0][i]=true;
            }
            else{
                flag=false;
            }
        }
        for(int i=1;i<=s1.length();i++){
            for(int j=1;j<=s2.length();j++){
                if(s3[i+j-1]==s1[i-1]&&m[i-1][j]){
                    m[i][j]=true;
                    continue;
                }
                 if(s3[i+j-1]==s2[j-1]&&m[i][j-1]){
                    m[i][j]=true;
                }
            }
        }
        return m[s1.length()][s2.length()];
    }
};