CODEWITHSUNDEEP
c
Headless Dev
Headless Dev

Reputation: 99

Selection Sort doesn't output as expected

I have this assignment for my C class. She gave us pseudo code for the selection sort. There's some other requisites, but those I don't need help with. I followed her code, and even looked online for sample code. And mine follows the same concept but it never works. When I print the "sorted" array, it prints the unsorted numbers and a bunch of other numbers. If I enter '8 7 6 5 4 3 2 1' my array prints '8765432146142368001234567846142368'.

#define MAXSIZE 10

void print_array(const int a[], int size);

int main()
{
   int get_numbers(int n[]); //Function to retrieve a list of numbers and 
   returns an array of the numbers

   int numbers[MAXSIZE]; //Array to store unsorted list of numbers

   void selection_sort(int a[], int size);

   puts("Enter each number then press enter. (Ctrl + Z) to end.");
   get_numbers(numbers);
   selection_sort(numbers, MAXSIZE);  
   print_array(numbers, MAXSIZE);
}

void get_numbers(int n[])
{
   int s; //Stores return value of scanf
   int i; //Stores amount of values entered

   for(i = 0; (s = scanf("%i", &n[i])) != EOF; i++);

   if(i == 0)
   {
      puts("Error: No numbers entered.");
   }else if(i > MAXSIZE)
   {
      puts("Error: Too many values entered.");
      print_array(n, MAXSIZE);
   }else
   {
      print_array(n, MAXSIZE);
   }
}

void print_array(const int a[], int size)
{
    for(int i = 0; i < size; i++)
    {
        printf("%i", a[i]);
    }
}

void selection_sort(int a[], int size)
{
   void swap(int n[], int i, int min_index);
   for(int i = 0; i < (size - 1); i++)
   {
      int min = a[i];
      int min_index = i;
      for(int j = (i + 1); j < size; j++)
      {
         if(a[j] < min)
         {
            min = a[j];
            min_index = j;
         }
      }
      swap(a, i, min_index);
   }
}

void swap(int n[], int i, int min_index)
{
    int temp = n[i];
    n[i] = n[min_index];
    n[min_index] = temp;
}

Upvotes: 0

Views: 59

Answers (2)

Headless Dev
Headless Dev

Reputation: 99

Thank you for everyone and their tips! I took what Bob Jarvis had mentioned (sorting based on exact number of values, spacing my output). My main problem was that it seemed to be printing a bunch of random numbers which I was unsure where it came from. After spacing I realized it does sort them but there was a random number ex. 8 7 6 5 4 3 2 1 44176288 0 1 2 3 4 5 6 7 8 44176288 0. After some more debugging I realized that I was also printing not at exact array size. After fixing all the different sizes it was fixed.

Upvotes: 0

Jake
Jake

Reputation: 78

There are quite a few issues with your program.

Function prototypes need to be declared before any other functions.

If they bail out early/late, you need to pass the value of i to print_array. If you pass MAXSIZE you will be reading/writing to memory that isn't yours. Which is why you get weird values.

Upvotes: 1

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