Very simple sort algorithm not working

Question

public static int[] sortArr(int[] a){
    int temp;
    for(int i = 0; i < a.length; i++){
        temp = a[i];
        a[i] = a[findMin(a, i)];
        a[findMin(a, i)] = temp;
    }
    return a;
}
public static int findMin(int[] a, int start){
    int min = a[start];
    int minIndex= start;
    for(int i = start; i < a.length; i++){
        if(a[i] < min){
            min = a[i];
            minIndex = i;
        }
    }
    return minIndex;
}

the sortArr method just returns the array that it is given, and I can't see why. I've worked it out on paper and it should be working. Can anybody see the problem?

Which variable do you return in findMin(), min or minIndex? — rdonuk
– rdonuk, Commented Mar 21, 2016 at 21:30
I just edited it, i return minIndex to find the location of the smallest value — Gabe Spound
– Gabe Spound, Commented Mar 21, 2016 at 21:35

Paul Hicks · Accepted Answer · 2016-03-21 21:40:47Z

6

You're calling findMin twice, but the code on the same line as the first call is causing the result of the second call to change.

You have:

a[i] = a[findMin(a, i)]; // findMin() returns the min, and you'll move that to a[i]
a[findMin(a, i)] = temp; // findMin() returns the new min == i

Instead use:

int min = findMin(a, i);
a[i] = a[min];
a[min] = temp;

edited Mar 21, 2016 at 21:40

answered Mar 21, 2016 at 21:32

Paul Hicks

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