Explication de ce programme simple - tri par seau

Question

Que fait int [] a dans ce code?

public class BucketSort_main { 

    public static void main(String[] args) { 
     int[] numbers = new int [5]; //create an array to house the numbers generated 
     int[] sortedArray = new int [5]; //create array to be a temp housing for the numbers 
     int [][] bucket = new int [10][numbers.length]; //creates 2D array of 0-9 
     int [] a = new int [10]; 
     int divisor = 1; 
     int digitCount = 1; 
     boolean moreDigits = true; 


     //fill the array and array to be sorted with the random numbers 0 - 100 
     for (int i = 0; i < numbers.length; i++) { 
      numbers [i] = (int)(Math.random()*100); 
      sortedArray [i] = numbers [i]; 
     } 


     System.out.println("UnSorted Numbers"); 

     for (int i = 0; i< numbers.length; i++){ 
      System.out.println (numbers[i]); 
     } 
    } 

    System.out.println("\n"); 

    int[] tempArray = new int[10]; //creatE a temp array of size equal to the amount of buckets 

    while (moreDigits) { 
     moreDigits = false; 

     for (int i = 0; i < tempArray.length; i++){ 
      tempArray[i]= -1; //initailze to make sure a null pointer is not hit 
     } 

     for (int i = 0; i < numbers.length; i++){ 
      int tmp = sortedArray[i]/divisor; //create a temp int of the array value/divisor to get its single digit value 

      if (tmp/10 != 0){ 
       moreDigits = true; 
      } 

      int numPlace = tmp % 10; 

      tempArray[numPlace] = sortedArray[i]; //at the digits "ones"/tens value for row index, set the number from the sorted array into that index 
      bucket [numPlace][a[numPlace]] = sortedArray[i]; //place the numbers into the proper coord of the bucket. 

      //Print statements used for DEBUGGING 
      System.out.println("Number: " + tempArray[numPlace] +" Has Digit "+digitCount+" equal to "+ numPlace); 

      // bucket [digit][a[digit]] = tempArray[i]; 

      //row may seem "off" to user, but the row prints based on 0 - n 
      System.out.println ("Digit " + numPlace + " moved into row " + a[numPlace] + ". " + bucket[numPlace][a[numPlace]]); 
      System.out.println (" "); 

      a[numPlace]++; 

     }  
     digitCount++; 
     divisor *= 10; //multipy the divisor by 10 to move to the next 1s. 10s, or 100s place 

     int j = 0; //iteration for tempNumbersArray 

     for (int x = 0; x < 10; x++) { 
      a[x] = 0; 
      for (int y = 0; y < numbers.length; y++){ 
       if (bucket[x][y] != 0) {//see if value in bucket is a zero, if it is dont print it 
        sortedArray [j] = bucket[x][y]; //set sorted array value equal to the value at row/col index of bucket 
        bucket[x][y] = 0; //set that spot that was just copied over to zero 
        j++; //increment to the next index of sorted array 
       }      
      } 
     } 
    } //end while 

    System.out.println("Sorted Numbers:"); 

    for (int i = 0; i < numbers.length; i++) { 
     System.out.println (sortedArray[i]); 
    } 
} 

Answer 1

Le tableau 'a' contient le nombre d'entrées que contient un certain compartiment. Chaque fois que quelque chose est ajouté au seau x, la valeur de a [x] est incrémentée de un.

Donc 'a' est seulement utilisé pour faire de la comptabilité. Cela peut être évité en changeant

bucket [numPlace][a[numPlace]] = sortedArray[i]; 

dans

bucket [numPlace][bucket[numPlace].length] = sortedArray[i]; 

et

System.out.println ("Digit " + numPlace + " moved into row " + a[numPlace] + ". " + bucket[numPlace][a[numPlace]]); 

dans

System.out.println ("Digit " + numPlace + " moved into row " + bucket[numPlace].length + ". " + bucket[numPlace][a[numPlace]]); 

et en enlevant

a[numPlace]++;