올바른 괄호 →예외★★ + count로 접근

나의 풀이

import java.util.*;
class Solution {
    boolean solution(String s) {
        Stack<Character> stack = new Stack<>();
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == '(') {
                stack.push(s.charAt(i));
            } else {
                try {
                    stack.pop();
                } catch (EmptyStackException e) {
                    return false;
                }
            }
        }
        return stack.isEmpty();
    }
}

 

 

 

다른사람의 풀이1

import java.util.Stack;
class Solution {
    boolean solution(String s) {
        boolean answer = true;  
        Stack<Character> st = new Stack<>();

        for (int i = 0; i < s.length(); i++) {
                if (s.charAt(i) == '(') {
                    st.push('(');
                } else if (s.charAt(i) == ')') {
                    if (st.isEmpty()) {
                        answer = false;
                        break;
                    } else {
                        st.pop();
                    }
                }
            }

            if(!st.isEmpty()) {

                answer = false;

            }

            
return answer;
    }   

}

 

 

 

 

다른사람의 풀이2

class Solution {
    boolean solution(String s) {
        boolean answer = false;
        int count = 0;
        for(int i = 0; i<s.length();i++){
            if(s.charAt(i) == '('){
                count++;
            }
            if(s.charAt(i) == ')'){
                count--;
            }
            if(count < 0){
                break;
            }
        }
        if(count == 0){
            answer = true;
        }

        return answer;
    }
}