How to get index of m smallest elements from an unsorted array, without changing the actual array?

问题:

I wanted to create a temporary array to store the input by the user and sort it to get the m smallest elements and refer to the original index of the originalArray and then print the index of the m smallest elements but when I run my code, all I get is -1. My elements should not be out of bounds of the original array as it is taken from originalArray. Why am I getting -1?

import java.util.*; public class MinimumSelection {     public static void main(String[] args)     {         //Array and variable declarations         int[] originalArray;         int[] tempArray;         int tempValue;         int lowestValue;         int arrayLength;         String elementValue;          //Prompt the user for random numbers as an array input         System.out.println("Please Enter your array length");         arrayLength = Integer.parseInt(new Scanner(System.in).nextLine());         //Input feeds as the length of the array as entered by user         originalArray = new int[arrayLength];         //Storing the input value in temporary array which will be used to sort         tempArray = new int[arrayLength];          //prompt user to enter elements of the orignial array         for (int element = 0; element < originalArray.length; element++)         {             System.out.printf("\n Enter array elements %1$s: " + "\r\n", element + 1);             elementValue = new Scanner(System.in).nextLine();             originalArray[element] = Integer.parseInt(elementValue);         }          System.arraycopy(originalArray, 0, tempArray, 0, originalArray.length);          //Sorting the original array         for (int write = 0; write < tempArray.length; write++)         {             for (int sort = 0; sort < tempArray.length - 1 - write; sort++)             {                 if (tempArray[sort] > tempArray[sort + 1])                 {                     tempValue = tempArray[sort + 1];                     tempArray[sort + 1] = tempArray[sort];                     tempArray[sort] = tempValue;                 }             }         }          //promoting user to enter no. of smallest elements they want this program to display         System.out.println("Please Enter number of smallest element");         lowestValue = Integer.parseInt(new Scanner(System.in).nextLine());          //display output         System.out.println("Result :");         for (int loop = 0; loop < lowestValue; loop++)         {             int x = tempArray[loop];             int y = Arrays.asList(originalArray).indexOf(x);             // Arrays.asList(array).indexOf(4);              System.out.println((new Integer(y)).toString());         }         new Scanner(System.in).nextLine();     } }

回答1:

Create a TreeMap where the key is the element and the value is its index in the original array. Then you iterate through the entries of this map and break out of the loop after the first m steps.

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