***Leetcode 87. Scramble String

参考后， 没做出来

class Solution {public:    bool isScramble(string s1, string s2) {        vector<int> v(127);        size_t n = s1.size();        if (n == 1) return s1[0] == s2[0];        for (size_t i = 0; i != n; ++i) {            ++v[s1[i]];            --v[s2[i]];        }        for (size_t i = 0; i != n; ++i) {            if (v[s1[i]] != 0) return false;        }        for (size_t i = 1; i != n; ++i) {            if (isScramble(s1.substr(0, i), s2.substr(0, i)) && isScramble(s1.substr(i, n - i), s2.substr(i, n - i)))                return true;            if (isScramble(s1.substr(0, i), s2.substr(n - i, i)) && isScramble(s1.substr(i, n - i), s2.substr(0, n - i)))                return true;        }        return false;    }};

class Solution {public:    bool isScramble(string s1, string s2) {        size_t n = s1.size();        if (n != s2.size()) return false;        vector<vector<vector<int> > >  flag(n, vector<vector<int> >(n, vector<int>(n + 1)));        for (size_t i = 0; i != n; ++i) {            for (size_t j = 0; j != n; ++j) {                if (s1[i] == s2[j]) flag[i][j][1] = 1;            }        }        for (size_t len = 2; len <= n; ++len) {            for (size_t i = 0; i != n; ++i){                for (size_t j = 0; j != n; ++j) {                    if (max(j, i) + len <= n) {                       for (size_t k = 1; k != len; ++k) {                            flag[i][j][len] = flag[i][j][len] || (flag[i][j + len - k][k] && flag[i + k][j][len - k]);                            flag[i][j][len] = flag[i][j][len] || (flag[i][j][k] && flag[i + k][j + k][len - k]);                        }                     }                }            }        }        return flag[0][0][n];    }};