This is my task. I googling for find out reason behind this function but can not find out. My teacher tell me what is the use of this function.

My Question is:

What is the purpose of the following function, assuming that the parameter size represents the size of the array data that's also passed as a parameter. Further assume that size is at least 2.

This is sample code he give me:

#include <stdio.h>

void procArray( int data[], int size ) {
     int temp = data[0];
     int index;
     for( index = 0; index < size - 1; index   )
     {
         data[index] = data[index   1];
         data[size-1] = temp;
         
         printf("%d ",   data[index]);
         printf("%d ",   data[size-1]);
     }
}

int main()
{
    int arr[2];
    procArray(arr, 2);

    return 0;
}

Every time i got random number in output like:

32767 -2102338448 

CodePudding user response：

The routine procArray appears to be written with the intent that it “rotate” the array one position “left,” meaning to modify the array such that, upon return from the function:

• The last element (index [size-1]) contains the value the first element (index [0]) the first element had upon calling the function.
• Each other element (index [i] for some i other than size-1) contains the value the element to its “right” (index [i 1]) had upon calling the function.

However, if this was the purpose, the function was written incorrectly. The statement data[size-1] = temp; should be after the loop, not inside it.

Further, the main routine fails to demonstrate how the function behaves because it fails to put values into arr.

A corrected function with a useful demonstration is:

#include <stdio.h>
#include <stdlib.h>


void procArray(int data[], size_t size)
{
     int temp = data[0];

     for (size_t i = 0; i < size-1;   i)
         data[i] = data[i 1];

     data[size-1] = temp;
}


int main(void)
{
    int arr[5] = {10, 11, 12, 13, 14};
    procArray(arr, 5);
    for (int i = 0; i < 5;   i)
        printf("arr[%d] = %d.\n", i, arr[i]);

    return 0;
}

This program outputs:

arr[0] = 11.
arr[1] = 12.
arr[2] = 13.
arr[3] = 14.
arr[4] = 10.

CodePudding user response：

It's because you array is not initialized.

In C, when you write int arr[2] your array is initialized with random value.

Your array doesn't have data in it, so the compiler doesn't know and set a random value.