Question

我正在做一个过去的CCC（加拿大计算竞赛）问题，我得到了一个奇怪的错误，当我将indexOf（）用于ArrayList中的整数时，它返回0。

以下是代码：

package problem4;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.concurrent.CopyOnWriteArrayList;

public class Problem4 {

    static List<Integer> totalnum = new CopyOnWriteArrayList<>();
    static ArrayList<Integer> div = new ArrayList<>();
    static String output = "";

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);

        try {
            int total = in.nextInt();
            for (int i = 0; i < total; i++) {
                totalnum.add(i + 1);
            }

            int roundnum = in.nextInt();
            for (int i = 0; i < roundnum; i++) {
                int tempnum = in.nextInt();
                div.add(tempnum);
            }

            print("cache org: " + totalnum.toString());
            for (int divnum : div) {
                for (int check : totalnum) {
                    print(check + " index: " + totalnum.indexOf(check));
                    if (totalnum.indexOf(check) % divnum == 0) {
                        totalnum.remove(totalnum.indexOf(check));
                    }
                }
                print("cache " + divnum + ": " + totalnum.toString());
            }

            String output = totalnum.toString().replace("[", "")
                    .replace("]", "").replace(",", "");

            for (int i = 0; i < output.length(); i++) {
                System.out.println(output.charAt(i));
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public static void print(String input) {
        System.out.println(input);
    }

}

这是输入/输出：

10
2
2
3
cache org: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
1 index: 0
2 index: 0
3 index: 0
4 index: 0
5 index: 0
6 index: 0
7 index: 0
8 index: 0
9 index: 0
10 index: 0
cache 2: []
cache 3: []

任何人都知道出了什么问题？

Answer 1

在每次迭代后删除第一个元素，以便下一个元素成为第一个元素。只需在每次迭代后打印数组内容：

 for (int divnum : div) {
     for (int check : totalnum) {
         print(check + " index: " + totalnum.indexOf(check));
         if (totalnum.indexOf(check) % divnum == 0) {
              totalnum.remove(totalnum.indexOf(check));
         }
         print("cache " + divnum + ": " + totalnum.toString());
     }
     print("cache " + divnum + ": " + totalnum.toString());
 }

然后，对于您的输入，您将看到此类输出

cache org: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
1 index: 0
cache org: [2, 3, 4, 5, 6, 7, 8, 9, 10]
2 index: 0
cache org: [3, 4, 5, 6, 7, 8, 9, 10]
3 index: 0
cache org: [4, 5, 6, 7, 8, 9, 10]
4 index: 0
cache org: [5, 6, 7, 8, 9, 10]
5 index: 0
cache org: [6, 7, 8, 9, 10]
6 index: 0
cache org: [7, 8, 9, 10]
7 index: 0
cache org: [8, 9, 10]
8 index: 0
cache org: [9, 10]
9 index: 0
cache org: [10]
10 index: 0
cache org: []
cache 2: []
cache 3: []

Java indexOf（int）返回0

1 个答案: