leetcode：Valid Parentheses

括号匹配

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.

class Solution {
public:
bool isValid(string s) {
//use stack
stack<char> st;
for(int i = 0;i<s.size();i++)
if(s[i] == ')' || s[i] == ']' || s[i] == '}')
{
if(st.empty())
return false;
else
{
char c = st.top();
st.pop();
if ((c == '(' && s[i] != ')') || (c == '[' && s[i] != ']') || (c == '{' && s[i] != '}'))
return false;
}
}
else
st.push(s[i]);
return st.empty();
}
};