Valid Parentheses

🔗 문제 링크

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

🔍 문제 설명

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.

⚠️ 제한사항

• $1 <= s.length <= 10^4$

• s consists of parentheses only '()[]{}'.

---

🗝 풀이 (언어 : Java)

과거에 두세번 풀어봤던 올바른 괄호 문제이다. stack을 이용해서 풀면 된다.

import java.util.Stack;

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