[leetcode 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.

[Solution]

使用堆栈进行配对即可.

bool isValid(string s)
{
stack<char> stk;
for (int i = 0; i < s.size(); i++)
{
switch(s[i])
{
case '(':
case '{':
case '[':
stk.push(s[i]);
break;
case ')':
if (stk.empty() || stk.top() != '(')
return false;
stk.pop();
break;
case ']':
if (stk.empty() || stk.top() != '[')
return false;
stk.pop();
break;
case '}':
if (stk.empty() || stk.top() != '{')
return false;
stk.pop();
break;
default:
return false;
}
}

return stk.empty();
}