面试金典--9.6

题目描述：实现一种算法，打印n对括号的全部有效组合

思路：递归，不合法状态就是right<left；其他情况加入左右括号分别递归

#include <iostream>
#include <queue>
#include <climits>
#include <algorithm>
#include <memory.h>
#include <stdio.h>
using namespace std;

vector<string> res;
void addParen(int left,int right,string ans)
{
    if(left <0 || right < left)
    {
        return;
    }
    if(left ==0 && right == 0)
    {
        res.push_back(ans);
        //return;
    }
    else
    {
        if(left > 0)
        {
            string ans1 = ans+'(';
            addParen(left-1,right,ans1);
        }
        if(right > left)
        {
            string ans1 = ans+')';
            addParen(left,right-1,ans1);
        }
    }
}

int main()
{
    string s;
    addParen(3,3,s);
    vector<string>::iterator it = res.begin();
    while(it != res.end())
    {
        cout<<*it<<endl;
        it++;
    }
    return 0;
}