leetcode-20-Valid Parentheses

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.
括号匹配，使用栈求解。

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