英文:
Index of number(s) in list in JAVA
问题
import java.util.ArrayList;import java.util.Scanner;public class IndexOf {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);ArrayList<Integer> list = new ArrayList<>();while (true) {int input = Integer.valueOf(scanner.nextLine());if (input == -1) {break;}list.add(input);}System.out.println("Search for? ");int src = scanner.nextInt();for (int i = 0; i < list.size(); i++) {int num = list.get(i);if (src == num) {System.out.println(src + " is at index " + i);}}}}
英文:
I need to have a program that asks the user for a number, and reports that number's index in the list. If the number is not found, the program should not print anything.
Example:
Sample Output:12334Search for? 33 is at index 23 is at index 3
This is what I have written but the put is looping multiple times. Can you suggest fixing it?
import java.util.ArrayList;import java.util.Scanner;public class IndexOf {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);ArrayList<Integer> list = new ArrayList<>();while (true) {int input = Integer.valueOf(scanner.nextLine());if (input == -1) {break;}list.add(input);}System.out.println("Search for? ");int src = scanner.nextInt();int ind = 0;for(int i=0; i<list.size(); i++){int num = list.get(i);if(src == num){ind = list.indexOf(src);}System.out.println(src + " is at index " + ind);}}}
EDIT
> Input: 1 2 3 3 4 -1
>
> Search for? 3 Output: 3 is at index 0 3 is at index 0 3 is at index 2 3 is at index 2 3 is at index 2 ///So it must be only one sentence for each index. Even if I put after "for" loop, it only output the first if index.
答案1
得分: 0
我能看到你代码中的一个问题，即你打印了所有的内容，而不仅仅是匹配的部分。为了解决这个问题，你需要将System.out.println放到if语句中，就像这样：
for(int i=0; i<list.size(); i++){int num = list.get(i);if(src == num){ind = i;System.out.println(src + " 在索引 " + ind);}}
如果还有其他问题，请告诉我。
英文:
I can see a single problem in your code, that is, you print everything, not only the matches. To solve that you need to put your System.out.println into the if, like this:
for(int i=0; i<list.size(); i++){int num = list.get(i);if(src == num){ind = i;System.out.println(src + " is at index " + ind);}}
Let me know if anything else was wrong.
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