Question

I am trying to write the following code using pointers and traversal by pointers instead of indexing (in C++).

The following code is correct:

void shift(int arr[], int n) {

int temp = arr[n - 1];

int temp1;

for (int i = 0; i < n; i++) {

temp1 = arr[i];

arr[i] = temp;

temp = temp1;

}

}

This is my ATTEMPT at writing it with pointers (and traversal by pointers!) but I know it is wrong. I believe the loop is correct but the body is wrong. Please remember int arr[] is an array. I cannot use indexing AT ALL. Pointers and traversal by pointers ONLY. Can someone help fix it?

void shift(int arr[], int n) {

int temp = arr + (n - 1);

int temp1;

for (int *ptr = arr; ptr < arr + n; ++ptr) {

temp1 = *ptr;

*ptr = temp;

temp = temp1;

}

}

Answer 1

The code given by you:

void shift(int arr[], int n) {

int temp = arr + (n - 1);

int temp1;

for (int *ptr = arr; ptr < arr + n; ++ptr) {

temp1 = *ptr;

*ptr = temp;

temp = temp1;

}

}

Modified code (without using indexing):

#include <iostream>

using namespace std;

void shift(int arr[], int n)

{

int *t1 = arr + n-1;

int temp;

//the shifting operation

for (int i = 0; i < n; i++) {

temp = *(arr+i);

*(arr+i) = *t1;

*t1 = temp;

}

//this loop traverses the array

for (int i = 0; i < n; i++)

cout<<*(arr+i);

}

//driver function

int main()

{

   int a[5]={1,2,3,4,5};

   shift(a,5);

   return 0;

}

OUTPUT:

24 //driver function 25 int main() 26 27 28 int a[5J-(1,2,3,4,5); 29 shift (a,5): 3 return ; 31 32 Get URL options compilation execution 51234 Exit code: (normal program termination)