BM60.java

package NiukeTOP101;

import java.util.ArrayList;

public class BM60 {
    public void recursion(int left, int right, String temp, ArrayList<String> res, int n){
        //左右括号都用完了，就加入结果
        if(left == n && right == n){
            res.add(temp);
            return;
        }
        //使用一次左括号
        if(left < n){
            recursion(left + 1, right, temp + "(", res, n);
        }
        //使用右括号个数必须少于左括号
        if(right < n && left > right){
            recursion(left, right + 1, temp + ")", res, n);
        }
    }
    public ArrayList<String> generateParenthesis (int n) {
        //记录结果
        ArrayList<String> res = new ArrayList<String>();
        //递归
        recursion(0, 0, "", res, n);
        return res;
    }
}