蜗牛慢慢爬 LeetCode 20. Valid Parentheses [Difficulty: Easy]

题目

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.

翻译

括号匹配

Hints

Related Topics: Stack, String

通过栈就可以简单实现了

代码

Java

class Solution {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<Character>();
        for(char c : s.toCharArray()){
            if(c == '(')    stack.push(')');
            else if(c=='[') stack.push(']');
            else if(c=='{') stack.push('}');
            else if (stack.isEmpty()||stack.pop()!=c)
                return false;
        }
        return stack.isEmpty();
    }
}

Python

class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        stack = []
        for i in range(len(s)):
            if s[i]=='(' or s[i]=='[' or s[i]=='{':
                stack.append(s[i])
            elif s[i]==')' or s[i]==']' or s[i]=='}':
                if len(stack)==0:   return False
                tmp = stack.pop()
                if (s[i]==')' and tmp!='(') or (s[i]==']' and tmp!='[') or (s[i]=='}' and tmp!='{'):
                    return False
        if len(stack)!=0:
            return False
        return True