无法使用指针访问数组中的某些值

Question

So I was asked to write a program which uses a pointer that points to the first element in an array and pass the pointer to a function. Then using only pointer variables (and looping constructs), print only the array values that are exact multiples of 7. Here's the script:

#include <iostream>
using namespace std;

void print_sevens(int *nums,int length){

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

    nums = nums + i;

       if(*nums % 7 == 0)
         cout << *nums << endl;

     }

}


int main() {

   int a[5]={7,49,2,8,70};
   int *p1 = &a[0];
   print_sevens(p1,5);

}

The output from this is :

7

49

-149462114

I can't find out what is wrong. Any help is appreciated. Thanks

Answer 1

nums is the pointer to the start of the array. You are reassigning it at every loop iteration to be nums + i , not nums + 1 . So, at the fourth iteration, for example, nums points to the initial array start + 0 + 1 + 2 + 3, which is the seventh element in your array of 5 elements. That's why you get garbage.

Use a subscript to make your life easy:

for(int i = 0; i < length; i++){
   if(nums[i] % 7 == 0)
       cout << nums[i] << endl;
 }