Sorting arrays descending

Question

I've recently learned how to sort arrays in ascending order with this code in Java;

int swapIndex,temp; 
for(int index=0; index<=array.length-2; index++) { 
    swapIndex = index; 
    for(int i=index+1; i<=array.length-1; i++) 
       if(array[i]<array[swapIndex]) swapIndex = i; 
    temp = array[index]; array[index] = array[swapIndex]; 
    array[swapIndex] = temp; 
  } 
}

Can somebody please tell me how to I can use this code but sort in descending order? Best regards

http://stackoverflow.com/questions/1694751/java-array-sort-descending — Thilo, Nov 14 '14 at 00:07

score 0 · Answer 1 · answered Nov 14 '14 at 00:02

0

Why don't you just use something like this instead?

Arrays.sort(array, Collections.reverseOrder());

answered Nov 14 '14 at 00:02

Christoffer

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1

There is no such method for primitive arrays. – Thilo Nov 14 '14 at 00:05
I'm not calling method from a primitive array. I'm calling it from the java.utils.Arrays class – Christoffer Nov 14 '14 at 00:08
1

Yes, and java.util.Arrays has no such method that takes a primitive array and a Comparator (because Comparator only works for Objects). – Thilo Nov 14 '14 at 00:09
Oh, yes your right. Then I guess he could convert the int[] to an Integer[] and then do some simple work on it. – Christoffer Nov 14 '14 at 00:14

score 0 · Answer 2 · answered Nov 14 '14 at 01:32

Just flip the sign in your if statement

int swapIndex,temp; 
for(int index=0; index<=array.length-2; index++) { 
    swapIndex = index; 
    for(int i=index+1; i<=array.length-1; i++) 
       if(array[i] > array[swapIndex]) swapIndex = i; //change the sign
    temp = array[index]; array[index] = array[swapIndex]; 
    array[swapIndex] = temp; 
  } 
}

This way, you're only swapping if the element at i is greater than the one at swapIndex, so the smaller numbers get moved further to the right.

Sorting arrays descending

2 Answers2