[string]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.

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