题解 | 括号配对问题

import java.util.Scanner;
import java.util.Stack;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        String input = in.nextLine();
        Stack<Character> stack = new Stack<>();

        boolean hasFlag = false;

        for (int i = 0; i < input.length(); i++) {
            char ch = input.charAt(i);
            if (ch == '[' || ch == '(' || ch == ']' || ch == ')') {
                if (ch == '[' || ch == '(') {
                    stack.push(ch);
                    hasFlag = true;
                    continue;
                }

                if (ch == ']') {
                    if (stack.size() > 0 && stack.lastElement() == '[') {
                        stack.pop();
                    } else {
                        System.out.println("false");
                        return;
                    }
                }
                if (ch == ')') {
                    if (stack.size() > 0 && stack.lastElement() == '(') {
                        stack.pop();
                    } else {
                        System.out.println("false");
                        return;
                    }
                }
            }
        }

        if (stack.size() == 0 && hasFlag) {
            System.out.println("true");
        } else {
            System.out.println("false");
        }
    }
}