LeetCode 20 Valid Parentheses (C++)

问题：

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.

提示：

Stack String

方法1：（效率低）

#include <stack>
#include <string>class Solution {
public:bool isValid(string s) {stack<char> mystack;for(int i=0; s[i]!='\0'; i++){char c=s[i];switch(c){case '(': case '[': case '{':mystack.push(c);break;case ')':if(mystack.empty() || mystack.top()!='(')return false;elsemystack.pop();break;case ']':if(mystack.empty() || mystack.top()!='[')return false;elsemystack.pop();break;case '}':if(mystack.empty() || mystack.top()!='{')return false;elsemystack.pop();break;}}return mystack.empty();}
};

方法2：（效率低）

#include <stack>
#include <string>class Solution {
public:bool isValid(string s) {stack<char> mystack;map<char,char> mymap;mymap.insert(pair<char,char>('(',')'));mymap.insert(pair<char,char>('[',']'));mymap.insert(pair<char,char>('{','}'));for(int i=0; s[i]!='\0'; i++){char c=s[i];switch(c){case '(': case '[': case '{':mystack.push(c);break;case ')': case ']': case '}':if(!mystack.empty()){if(c!=mymap[mystack.top()])return false;mystack.pop(); //pop()的返回值为void
                    }elsereturn false;break;}}return mystack.empty();}
};

该题别人用Java写的：https://segmentfault.com/a/1190000003481208

C++栈的申明：http://zhidao.baidu.com/link?url=DvEEXh4U47QLJnjmv6rAeMVk1V7A_5LCii42ctj8m2ehl1MepSy0w9BSWevmfuHwlstx0D60kvBNRvAoQgFtjK

C++栈操作：http://www.169it.com/article/2839007600903800247.html

C++ map操作：http://blog.sina.com.cn/s/blog_61533c9b0100fa7w.html

转载于:https://www.cnblogs.com/calvin2/p/5964633.html

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