Solution2.cs

public class Solution {
    public bool IsScramble(string s1, string s2) {
        int n = s1.Length;
        bool[,,] f = new bool[n, n, n + 1];
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++ j) {
                f[i, j, 1] = s1[i] == s2[j];
            }
        }
        for (int k = 2; k <= n; ++k) {
            for (int i = 0; i <= n - k; ++i) {
                for (int j = 0; j <= n - k; ++j) {
                    for (int h = 1; h < k; ++h) {
                        if (f[i, j, h] && f[i + h, j + h, k - h]) {
                            f[i, j, k] = true;
                            break;
                        }
                        if (f[i, j + k - h, h] && f[i + h, j, k - h]) {
                            f[i, j, k] = true;
                            break;
                        }
                    }
                }
            }
        }
        return f[0, 0, n];
    }
}