LeetCode--87. Scramble String

87. Scramble String
暴力递归算法：

class Solution {
    
    
    public boolean isScramble(String s1, String s2) {
        
        if(s1.length()!=s2.length())
            return false;
        if (s1.equals(s2)) return true;
        int[] record=new int[26];
        for(int i=0;i<s1.length();i++)
        {
            record[s1.charAt(i)-'a']++;
        }
        
        for(int i=0;i<s2.length();i++)
        {
            record[s2.charAt(i)-'a']--;
        }
        
        for(int i=0;i<26;i++)
        {
            if(record[i]!=0)
                return false;
        }
        
        for(int i=1;i<s1.length();i++)
        {
            if( (isScramble(s1.substring(0,i),s2.substring(0,i)) && isScramble(s1.substring(i),s2.substring(i))) ||
                (isScramble(s1.substring(0,i),s2.substring(s2.length()-i)) && isScramble(s1.substring(i),s2.substring(0,s2.length()-i))))
                return true;
        }
        return false;
        
    }

动态规划：

public class Solution {
	public boolean isScramble(String s1, String s2) {
        if (s1 == null || s2 == null) return false;
        int m = s1.length();
        int n = s2.length();
        if (m != n) return false;

        boolean[][][] dp = new boolean[m][m][m+1];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < m; j++) {
                dp[i][j][1] = s1.charAt(i) == s2.charAt(j);
            }
        }

        for (int k = 2; k <= m; k++) {
            for (int i = 0; i <= m - k; i++) {
                for (int j = 0; j <= m - k; j++) {
                    dp[i][j][k] = false;
                    for (int part = 1; part < k; part++) {
                        if ((dp[i][j][l] && dp[i+l][j+l][k-l])
                                || (dp[i][j+k-l][l] && dp[i+l][j][k-l])) {
                            dp[i][j][k] = true;
                        }
                    }
                }
            }
        }
        return dp[0][0][s1.length()];
    }
}