题解 | #删除字符串中出现次数最少的字符#

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.hasNextInt()) { // 注意 while 处理多个 case
        //     int a = in.nextInt();
        //     int b = in.nextInt();
        //     System.out.println(a + b);
        // }
        String line = in.nextLine();
        Node[] nodes = new Node[line.length()];
        int index = 0;
        // char[] minChar = new char[line.length()];
        for (int i = 0; i < line.length(); i++) {
            char c = line.charAt(i);
            boolean has = false;
            for (int j = 0; j < index; j++) {

                if (nodes[j].c == c) {
                    nodes[j].n++;
                    has = true;
                    break;
                }
            }
            if (has) {
                continue;
            } else {
                Node node = new Node();
                node.c = c;
                nodes[index] = node;
                index++;
            }
        }
        for (int i = 1; i <= 20; i++) {

            boolean find = false;
            for (int j = 0; j < nodes.length; j++) {
                if (nodes[j] == null) {
                    break;
                }
                if (i == nodes[j].n) {
                    line = line.replaceAll(Character.toString(nodes[j].c), "");
                    find = true;
                }
            }
            if (find) {
                break;
            }

        }
        System.out.print(line);
    }

}
class Node {
    protected char c;
    protected int n = 1;
}