[leetcode]Scramble String

class Solution {
public:
bool isScramble(string s1, string s2) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int N = s1.size();
if(N != s2.size()) return false;
if(N == 0) return s1 == s2;

vector<vector<vector<bool>>> f(N, vector<vector<bool>>(N, vector<bool>(N+1, false)));

for(int i = 0; i < N; i++){
for(int j = 0; j < N; j++){
f[i][j][1] = (s1[i] == s2[j]);
}
}

bool tmp;

for(int len = 2; len <= N; len++){
for(int i = 0; i < N; i++){
for(int j = 0; j < N; j++){
for(int k = 1; k < len; k++){
if(i+k >= N || j+k >= N || j+len-k >= N) continue;

tmp = f[i][j][k] && f[i+k][j+k][len-k] || f[i][j+len-k][k] && f[i+k][j][len-k];
if(tmp){
f[i][j][len] = true;
break;
}
}
}
}
}

return f[0][0]
;

}
};