题解 | 完成括号匹配

import java.util.Scanner;

// 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
        while (in.hasNext()) {
            String input = in.nextLine();
            // 处理字符串并输出结果
            System.out.println(makeBracketsBalanced(input));
        }
        in.close();
    }

    public static String makeBracketsBalanced(String s) {
        int openBrackets = 0;
        int missingOpen = 0;

        // 遍历字符串，统计左括号和需要补充的左括号数量
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (c == '[') {
                openBrackets++;
            } else if (c == ']') {
                if (openBrackets == 0) {
                    missingOpen++;
                } else {
                    openBrackets--;
                }
            }
        }

        // 构建最终结果字符串
        StringBuilder result = new StringBuilder();
        // 补充缺失的左括号
        for (int i = 0; i < missingOpen; i++) {
            result.append('[');
        }
        result.append(s);
        // 补充缺失的右括号
        for (int i = 0; i < openBrackets; i++) {
            result.append(']');
        }

        return result.toString();
    }
}