generate-parentheses

/**
*
* @author gentleKay
* 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:
* "((()))", "(()())", "(())()", "()(())", "()()()"
*
* 给定n对括号，编写一个函数来生成格式良好的括号的所有组合。
* 例如，给定n=3，解集为：
* "((()))", "(()())", "(())()", "()(())", "()()()"
*/

　　

import java.util.ArrayList;

/**
 * 
 * @author gentleKay
 * 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:
 * "((()))", "(()())", "(())()", "()(())", "()()()"
 * 
 * 给定n对括号，编写一个函数来生成格式良好的括号的所有组合。
 * 例如，给定n=3，解集为：
 *  "((()))", "(()())", "(())()", "()(())", "()()()"
 */

public class Main30 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println(Main30.generateParenthesis(3));
	}
	
	public static ArrayList<String> generateParenthesis(int n) {
		ArrayList<String> list = new ArrayList<>();
		String str = "";
		generate(list, n, n,str);
		return list;
    }
	
	public static void generate(ArrayList<String> list, int left, int right, String str) {
		if (left == 0 && right == 0) {
			list.add(str);
			return ;
		}
		if (left > 0) {
			generate(list, left-1,right, str+'(');
		}
		if (right > left) {
			generate(list,left,right-1, str+')');
		}
	}
}