[Codility] Stacks and Queues - Nesting / Java

1. 문제

A string S consisting of N characters is called properly nested if:

• S is empty;
• S has the form "(U)" where U is a properly nested string;
• S has the form "VW" where V and W are properly nested strings.

For example, string "(()(())())" is properly nested but string "())" isn't.

Write a function:

class Solution { public int solution(String S); }

that, given a string S consisting of N characters, returns 1 if string S is properly nested and 0 otherwise.

For example, given S = "(()(())())", the function should return 1 and given S = "())", the function should return 0, as explained above.

Write an efficient algorithm for the following assumptions:

• N is an integer within the range [0..1,000,000];
• string S consists only of the characters "(" and/or ")".

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2. 코드

import java.util.*;

class Solution {
    public int solution(String S) {
        
        Stack<Character> stack = new Stack<>();
        
        for(int i=0; i<S.length(); i++) {
            char c = S.charAt(i);
            
            if(c == '(') {
                stack.add(c);
            } else if(c == ')') {
                if(stack.isEmpty())
                    return 0;
                
                stack.pop();
                
            }
        }
        
        if(stack.size() > 0)
            return 0;
        else
            return 1;
    }
}