我如何排序2个并行数组

Question

I have 2 arrays, 1 1dimensional and another 2dimensional that i have to sort. The problem is that I don't know how to sort them in parallel. I already sorted the 1d array according to alphabetical order but I want to sort the 2d array accordingly. So I need to send these two arrays to a sort function that will return the two arrays sorted in ascending order while the elements in the 1d array "arr1" keep their corresponding elements in the 2d array "arr2".

What I have so far:

import java.io.*;
import java.util.Scanner;
import java.util.Arrays;

public class JAVAhw15 {
public static void main(String args[]) throws IOException {

//required for input    
BufferedReader usrInput = new BufferedReader(
new InputStreamReader(System.in));

Scanner user_input = new Scanner( System.in );

int row = 10;
int col = 3;
int size = 10;

//Declare & Initialize
int arr2[][] = new int[row][];
String arr1[] = new String[size];

//construct 2d arr
for(int i=0; i<row; i++)
{
    arr2[i] = new int[col];
}

//Filling 1d array arr1
System.out.println("Enter 10 names please: ");
for(int i=0; i<size; i++)
{
    arr1[i] = user_input.next();
}


//Filling 2d array arr2
System.out.println("Enter 3 telephone numbers for each name entered");
for(int i=0; i<row; i++)
{
    for(int j=0; j<col; j++)
    {
        System.out.println(arr1[i]+"'s Tel "+j+" is: ");
        arr2[i][j] = Integer.parseInt(usrInput.readLine());
    }
}

System.out.println("After sort :");

    String merged[] = new String[arr1.length];
    for (int i=0; i< arr1.length; i++) {
        merged[i] = arr1[i]+"=="+arr2[i];
    }
    Arrays.sort(merged);
    for(int i = 0; i < merged.length; i++) {
    System.out.println( (i+1) + ". "+
    merged[i].split("==")[0] + "\t\t" +   
    merged[i].split("==")[1]);
    }
}
}

Answer 1

I can see two solutions :

• you create a class that merges the data you are storing in two separate lists. This way, you will have only one list and it will be easier for you to do waht you want.

• you write yourself a classical sort like quick sort, with a small variant : you will not only sort the aray but also return an object representing the permutation that was applied to the array to sort it. Then, you just have to write a method to apply the permutation on the other array.

I would prefer the first solution but since you've shown interest for the second one, here is an example of how you can do it :

import java.util.Arrays;
import java.util.Random;

public class QuickSort {
    private static Random   rd = new Random();

    public static <T extends Comparable<T>> Integer[] sort(T[] arr) {
        Integer[] perm = new Integer[arr.length];
        for (int i=0 ; i<perm.length ; i++)
            perm[i] = i;
        sort(arr,perm,0,arr.length - 1);
        return perm;
    }

    private static <T extends Comparable<T>> void sort(T[] arr, Integer[] perm, int start, int end) {
        if (start < end) {
            int index = pivot(arr,perm,start,end);
            sort(arr,perm,start,index - 1);
            sort(arr,perm,index + 1,end);
        }
    }

    private static <T extends Comparable<T>> int pivot(T[] arr, Integer[] perm, int start, int end) {
        int index  = start + rd.nextInt(end - start + 1);
        T   pivot  = arr[index];
        int result = start;
        swap(arr,perm,index,end);

        for (int i=start ; i<end ; i++) 
            if (arr[i].compareTo(pivot) < 0) 
                swap(arr,perm,i,result++);
        swap(arr,perm,result,end);
        return result;
    }

    private static <T> void swap(T[] arr, Integer[] perm, int i, int j) {
        swap(arr,i,j);
        swap(perm,i,j);
    }

    private static <T> void swap(T[] arr, int i, int j) {
        T tmp  = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;       
    }

    public static void main(String[] args) {
        Integer[] arr = { 1,3,4,6,9,2,8 };
        Integer[] res = sort(arr);
        System.out.println("sorted array : " + Arrays.toString(arr) + ", permutation : " + Arrays.toString(res));
     }
}