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输出括号所有合法匹配

原文链接:http://blog.csdn.net/doc_sgl/article/details/8917476

简答题最后一题,编程实现所有括号的合法匹配

如输入3

输出:"((()))”, “(()())”, “(())()”, “()(())”, “()()()”

 

思路:深搜+剪枝,关键在于记录已经用掉的左括号个数和右括号的个数,

1,当用过的左括号个数小于右括号则非法;

2,当二者个数和大于2N则非法;

3,当二者个数相等且数目等于2N此时输出。

#include <iostream>using namespace std;void DFS_bracket(char* str,int n, int left_used, int right_used){    if(left_used == right_used && left_used + right_used == 2*n)    {        for(int i = 0; i < left_used*2; ++i)            cout<<str[i];        cout<<endl;        return;    }    if(left_used < right_used || left_used + right_used >= 2*n)    {        return ;    }    int index = left_used + right_used;    str[index] = (;    DFS_bracket(str, n, left_used + 1, right_used);     str[index] = );    DFS_bracket(str, n, left_used, right_used + 1);}int main(){    int parenthesisnum;    cin>>parenthesisnum;    char* str = new char[parenthesisnum*2+1];    DFS_bracket(str,parenthesisnum,0,0);    return 0;}

 

输出括号所有合法匹配