[LeetCode]Valid Parentheses

题目描述:(链接)

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.

解题思路:

用一个stack实现

class Solution {
public:
bool isValid(string s) {
for (int i = 0; i < s.size(); ++i) {
switch (s[i]) {
case '(':
case '{':
case '[': {
cache.push(s[i]);
break;
}
case ')': {
if (!isSuitable('(')) {
return false;
}
break;
}
case '}': {
if (!isSuitable('{')) {
return false;
}
break;
}
case ']': {
if (!isSuitable('[')) {
return false;
}
break;
}
}
}

if (!cache.empty()) return false;

return true;
}
private:
stack<int> cache;
bool isSuitable(int character) {
if (cache.empty()) {
return false;
}

int ch = cache.top();
if (ch != character) {
return false;
}

cache.pop();

return true;
}
};