开始刷leetcode day20：Generate Parentheses

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:

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

Java:

public class Solution {

public ArrayList<String> generateParenthesis(int n) {

ArrayList<String> list = new ArrayList<String>();

generate("",0,0,list,n);

return list;

}

public void generate(String current, int left, int right,ArrayList<String> list, int n)

{

if(left < right) return;

if(left == n && right == n)

{

list.add(current);

return;

}else if(left==n)

{

generate(current+")",left,right+1,list,n);

return;

}

generate(current+"(",left+1,right,list,n);

generate(current+")",left, right+1,list,n);

return;

}

}