leetcode-algorithms-20 Valid Parentheses
leetcode-algorithms-20 Valid Parentheses
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
An input string is valid if:
Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.
Note that an empty string is also considered valid.
Example 1:
Input: "()"
Output: true
Example 2:
Input: "()[]{}"
Output: true
Example 3:
Input: "(]"
Output: false
Example 4:
Input: "([)]"
Output: false
Example 5:
Input: "{[]}"
Output: true
解法
通过栈实现匹配.
class Solution
{
public:
bool isValid(string s)
{
std::stack<char> matchs;
for (int i = 0; i < s.size(); ++i)
{
switch(s[i])
{
case '(':
case '{':
case '[':
matchs.push(s[i]);
break;
case ')':
if (matchs.size() <= 0 || matchs.top() != '(') return false;
matchs.pop();
break;
case '}':
if (matchs.size() <= 0 || matchs.top() != '{') return false;
matchs.pop();
break;
case ']':
if (matchs.size() <= 0 || matchs.top() != '[') return false;
matchs.pop();
break;
}
}
return matchs.empty();
}
};
