Selection Sort setting wrong values in C

Question

New programmer here! I am implementing selection sort, with a max variable instead of the usual min, but I still want to sort from lowest to highest. The code below sorts the list perfectly except for the first value which it makes a very large negative number... Any tips for what I can fix to get it sorting properly?

void selection(int Array[], int size) {
   int i, j, max, temp;
   for (i = 0; i < size-1; i++) {
     max = i;
       for (j = i+1; j <= size; j++) {
          if ( Array[j] < Array[max] )
             max = j;
       }
       temp = Array[max];
       Array[max] = Array[i];
       Array[i] = temp;
   }
}

You step outside the bounds of the array with for (j = i+1; j <= size; j++) { — it should be < not <=. — Jonathan Leffler
– Jonathan Leffler, Commented Feb 13, 2020 at 18:26

Jonathan Leffler · Accepted Answer · 2020-02-13 18:27:10Z

5

for(j = i+1; j<=size; j++)

This line is your problem. You are accessing one past the end of the array, which will be undefined behavior and can often give you weird values. Change the condition to j < size.

edited Feb 13, 2020 at 18:27

Jonathan Leffler

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answered Feb 13, 2020 at 18:26

Tyler

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Comments

executable · Accepted Answer · 2020-02-13 18:47:37Z

1

In the above lines of code I can see that you are using 0 based indexing for the array, hence when you are referring to Array[size] or Array[size+1] this throws garbage values, you should replace the inner loop to

for (j = i+1; j < size; j++)

answered Feb 13, 2020 at 18:47

executable

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