本題源自LeetCode

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例如

s1 ="aabcc",
s2 ="dbbca",

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

轉自大佬的思路：動態規劃。http://www.jianshu.com/p/1e991930e44f

自己做了實現：

    bool isInterleave(string s1, string s2, string s3) {
        int len1=s1.length();
        int len2=s2.length();
        int len3=s3.length();
        
        if(len1+len2!=len3)
            return false;
        vector<vector<bool>> dp(len1+1,vector<bool>(len2+1));
        dp[0][0]=true;
        for(int i=1;i<=len1;i++){
            dp[i][0]=dp[i-1][0]&&s1[i-1]==s3[i-1];
        }
        for(int j=1;j<=len2;j++)
            dp[0][j]=dp[0][j-1]&&s2[j-1]==s3[j-1];
        
        for(int i=1;i<=len1;i++){
            for(int j=1;j<=len2;j++){
                dp[i][j]=dp[i-1][j]&&s1[i-1]==s3[i-1+j] || dp[i][j-1]&&s2[j-1]==s3[i+j-1];
            }
        }
        return dp[len1][len2];
    }