leetCode 20. Valid Parentheses 字符串

20. Valid Parentheses

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.题目大意：
括号匹配问题。
思路：
采用压栈出栈来处理。

class Solution {
public:
bool isValid(string s) {
if(s.size() == 0 || s.size() % 2 == 1)
return false;
map<char, char> brackets;
brackets.insert(pair<char, char>('}', '{'));
brackets.insert(pair<char, char>(']', '['));
brackets.insert(pair<char, char>(')', '('));
stack<char> mystack;
for(int i = 0 ;i < s.size();i++)
{
if(s[i] == '{' || s[i] == '[' || s[i] == '(' )
{
mystack.push(s[i]);
}
else
{
if( mystack.size() < 1)
return false;
if(brackets[s[i]] == mystack.top())
mystack.pop();
else
return false;
}
}
if(mystack.size() == 0)
return true;
else
return false;
}
};

2016-08-11 00:30:15