按照规则生成括号

 

import java.util.*;

 

public class Solution {

/**

*

* @param n int整型

* @return string字符串ArrayList

*/

static ArrayList<String> ans = new ArrayList<>();

public static ArrayList<String> generateParenthesis(int n) {

char[] path = new char[n * 2];

dfs(0, 0, n, path, 0);

return ans;

}

private static void dfs(int left, int right, int n, char[] path, int index) {

if (left + right == 2 * n) {

ans.add(new String(path));

return;

}

if (left < n) {

path[index] = '(';

dfs(left + 1, right, n, path, index + 1);

}

if (left > right) {

path[index] = ')';

dfs(left, right + 1, n, path, index + 1);

}

}

}