LeetCode - 20. Valid Parentheses(String, Stack)*

문제

Given a string s 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.
Every close bracket has a corresponding open bracket of the same type.

https://leetcode.com/problems/valid-parentheses/

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

풀이

class Solution {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<>();
        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();
    }
}