题解 | #完成括号匹配#

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 sc = new Scanner(System.in);
        String s = sc.nextLine();
        Stack<Character> stack = new Stack<Character>();
        for (char c : s.toCharArray()
            ) {
            if (c == ']' && !stack.isEmpty() && stack.peek() == '[') {
                stack.pop();
            } else {
                stack.push(c);
            }
        }
        int l = 0;
        int r = 0;
        while (!stack.isEmpty()) {
            if (stack.peek() == '[') {
                l ++;
            } else r ++;
            stack.pop();
        }
        for (int i = 0; i < r; i++) {
            System.out.print("[");
        }
        System.out.print(s);
        for (int i = 0; i < l; i++) {
            System.out.print("]");
        }
    }
}

这类符号匹配问题还是用栈进行匹配比较好使