LeetCode | Generate Parentheses

题目

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

For example, given n = 3, a solution set is:

"((()))", "(()())", "(())()", "()(())", "()()()"

分析

递归生成结果，注意判断条件。

代码

import java.util.ArrayList;

public class GenerateParentheses {
	public ArrayList<String> generateParenthesis(int n) {
		ArrayList<String> list = new ArrayList<String>();
		char[] array = new char[2 * n];
		solve(list, array, 0, 0, n);
		return list;
	}

	private void solve(ArrayList<String> list, char[] array, int left,
			int right, int n) {
		if (left == n && right == n) {
			list.add(new String(array));
		}
		if (right < left) {
			array[left + right] = ')';
			solve(list, array, left, right + 1, n);
		}
		if (left < n) {
			array[left + right] = '(';
			solve(list, array, left + 1, right, n);
		}
	}
}