Question

希望你们都过得愉快。我试图从一组大小为n的数字（从用户输入）返回第二大值的索引。我能够找到最大值以及第二大值，但似乎每当我尝试输出int类型的secondLargestIndex变量时，无论我做什么，它总是= 0表示输出。我已经使用变量largestIndex和secondLargestIndex更新了算法中的索引，并将它们放在整个程序的全局范围内（在main方法中），所以如果我没有弄错的话，变量会在全局范围内不断更新随着程序的运行。没有重复的任何变量让我更加确定，这就是为什么我很困惑。我跟踪它们并在适当时修改它们，同时跟踪值，但仍然输出0.如果你可以查看我的代码并提供一些反馈，我会非常感激。感谢您抽出宝贵时间帮助我。

import java.util.*;

public class hwk3_1 {

/*  write an algorithm to find the 2nd largest element in a set containing n entries
 */

public static void main( String[] args) {

    // declare needed variables
    int[] arr;
    int largest = 0, second_largest = 0, n = 0, largestIndex = 0, 
secondLargestIndex = 0;

Scanner input = new Scanner(System.in);

    // prompt user for size n
    System.out.print("Please enter the size of your array: ");
    n = input.nextInt();
    arr = new int[n];

    // take in input of size n from user
    System.out.print("Please enter your set of int values: ");
    for(int i = 0; i < n; i++){
        arr[i] = input.nextInt();
    }

    // display to user their set of numbers
    System.out.println("You entered: " + Arrays.toString(arr));

    // output to the user what the 2nd largest number is
    System.out.println("Second largest is: " + secondLargest(arr, largest, 
second_largest, largestIndex, secondLargestIndex));
    System.out.println("Second largest Index is: " + 
findIndex_2ndLargest(arr, second_largest));

}// end main

// method secondLargest
public static int secondLargest(int[] arr, int largest, int second_largest, 
int largestIndex, int secondLargestIndex) {

    // traverse array to find 2nd largest num
    for (int i = 0; i < arr.length; i++) {

        // if the current index's value is greater than current largest, 
then modify max & max2
        if (largest < arr[i]) {
            second_largest = largest;
            secondLargestIndex = largestIndex;
            largest = arr[i];
            largestIndex = i;
        // now we can traverse and see whether if there is a num larger than 
2ndmax
        } else if (second_largest < arr[i])
            second_largest = arr[i];
            secondLargestIndex = i;

    }// end for loop

    return second_largest;

}// end method secondLargest

// find the index of the second largest num
public static int findIndex_2ndLargest(int[] arr, int secondLargest){
    int index = 0;
    for(int i = 0; i < arr.length; i++){
        if(arr[i] == secondLargest)
            index = i;
    }

    return index;
    }

}

我的输出 请输入您的阵列大小：5 请输入您的int值集：5 4 3 2 1 你输入了：[5,4,3,2,1] 第二大是：4 第二大指数是：0

渴望输出 请输入您的阵列大小：5 请输入您的int值集：5 4 3 2 1 你输入了：[5,4,3,2,1] 第二大是：4 第二大指数是：1

Java：如何返回第二大数字的索引？能够返回值，返回索引常常= 0

0 个答案: