题目：

题解：

class Solution {
public:bool isInterleave(string s1, string s2, string s3) {auto f = vector <int> (s2.size() + 1, false);int n = s1.size(), m = s2.size(), t = s3.size();if (n + m != t) {return false;}f[0] = true;for (int i = 0; i <= n; ++i) {for (int j = 0; j <= m; ++j) {int p = i + j - 1;if (i > 0) {f[j] &= (s1[i - 1] == s3[p]);}if (j > 0) {f[j] |= (f[j - 1] && s2[j - 1] == s3[p]);}}}return f[m];}
};