leetcode_20题——Valid Parentheses（string，stack堆栈）

Valid Parentheses

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Question Solution

Given a string containing just the characters ‘(‘, ‘)‘, ‘{‘, ‘}‘, ‘[‘ and ‘]‘, determine if the input string is valid.

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

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#include<iostream>
#include<string>
#include <stack>
using namespace std;

char change_char(char a)
{
	switch(a)
	{
	case ‘(‘:{return ‘)‘;break;}
	case ‘)‘:{return ‘(‘;break;}
	case ‘{‘:{return ‘}‘;break;}
	case ‘}‘:{return ‘{‘;break;}
	case ‘[‘:{return ‘]‘;break;}
	case ‘]‘:{return ‘[‘;break;}
	}
}
/*采用堆栈的方法，在是前括号时将其压入到堆栈中，是反括号时进行匹配
*/
bool isValid(string s) {
	stack<char> str_temp;
	if(s[0]==‘(‘||s[0]==‘[‘||s[0]==‘{‘)
		str_temp.push(s[0]);
	else
		return 0;

	int i=1;
	int len=s.size();
	while(i<len)
	{
		if(s[i]==‘(‘||s[i]==‘[‘||s[i]==‘{‘)//是前括号
		{str_temp.push(s[i]);i++;}
		else//是反括号
		{
			if(str_temp.empty())//栈里为空
				return 0;
			else
			{
				if(str_temp.top()!=change_char(s[i]))//不匹配
					return 0;
				str_temp.pop();
				i++;
			}
		}
	}
	if(str_temp.empty())//栈中是否为空
		return 1;
	else
		return 0;
}
int main()
{
	string s="()";
	cout<<isValid(s)<<endl;
	system("pause");
	return 1;
}