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:

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

public class Solution {
    public List<String> generateParenthesis(int n) {
        int left=0;
        int right=0;
        String str="";
        List<String> list =new ArrayList<String>();
        gen(left, right, n, str, list);
        return list;
    }
    public void gen(int left, int right, int n, String str, List<String> list){
    	if( left==n && right==n){
    		list.add(str);
    		return;
    	}
    	
    	if( left<n && left==right){
    		 gen(left+1, right, n,str+"(", list);
    	}
    	else if( left<n && left>right ){
    		gen(left+1, right, n,str+"(", list);
    		gen(left, right+1, n,str+")", list);
    	}
    	else if(left==n && right<n ){
    		gen(left, right+1, n,str+")", list);
    	}
    }
}

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Generate Parentheses

原文：http://blog.csdn.net/dutsoft/article/details/37700647