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C: Reversing order of array elements using pointer syntax

 
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C: Reversing order of array elements using pointer syntax
Emper0r
6 Jun, 2007 - 11:35 AM
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Hey guys, basically what I'm trying to do is make a function that takes two arguments, an array of int’s and the number of elements in the array. Then the function is supposed reverse the order of the array elements. However, I'm needing to use only pointer syntax, this means no []'s. Here's what I have so far, if anyone can tell me how exactly I would reverse the order I would greatly appreciate it.

CODE

void reverseArray (int *arr, int nElts)
{
    int i;
    arr=(int*)malloc(nElts*sizeof(int));
    for (i = nElts - 1; i > 0; i--)
      
}
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Algorythm
RE: C: Reversing Order Of Array Elements Using Pointer Syntax
6 Jun, 2007 - 12:38 PM
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Set two pointers: one to the end and one to the beginning. Then move them toward each other, swapping the contents as you go. When the two pointers point to the same place, you're done.
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rameshg87
RE: C: Reversing Order Of Array Elements Using Pointer Syntax
7 Jun, 2007 - 03:14 AM
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Well the code that Algorythm said, that should be just like this. i and j are scan throught the array, end is the end address of the array. In pointer arithmetic, for an integer pointer i in C, i++ means to increment the content inside the pointer i be sizeof(int).

CODE

void reverseArray (int *arr, int nElts)
{
    int *i,*j,temp,*end;
    if(nElts>0)
        end=arr+(nElts-1);
    for (i=arr,j=end;j>i;j--,i++)
        {
            temp=*i;
            *i=*j;
            *j=temp;
        }
}


This post has been edited by rameshg87: 7 Jun, 2007 - 07:47 AM
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