Question

using C++ only.

The findFirstZero function is supposed to find the first element in an array whose value is zero, and sets the parameter  p to point to that element, so the caller can know the location of that element holding the value zero. Explain why this function won't do that, and show how to fix it. Your fix must be to the function only; you must not change the  main routine below in any way. As a result of your fixing the function, the main routine below needs to work correctly.

  #include <iostream>
using namespace std;

void findFirstZero(int arr[], int n, int* p)
{
p = nullptr; /// default value if there isn't a 0 in the array at all
for (int k = n - 1; k >= 0; k--)
{
if (arr[k] == 0) // found an element whose value is 0
// since we want the first zero value, as we keeping looping, we'll get to the 0 that is behind us in the array...
{
p = arr + k; // change the value of p
}
}
}       

int main()
{
int nums[6] = { 10, 20, 0, 40, 30, 50 };
int* ptr = nullptr;

findFirstZero(nums, 6, ptr);
if (ptr == nullptr)
{
cout << "The array doesn't have any zeros inside it." << endl;
}
else
{
cout << "The first zero is at address " << ptr <<  endl;
cout << "It's at index " << ptr - nums << endl;
cout << "The item's value is " << *ptr << " which is zero! I found it." << endl;
}
return( 0 );
}

Answer 1

#include <iostream>
using namespace std;

//we need to pass it as pass by reference
void findFirstZero(int arr[], int n, int*& p)
{
p = nullptr; /// default value if there isn't a 0 in the array at all
for (int k = n - 1; k >= 0; k--)
{
if (arr[k] == 0) // found an element whose value is 0
// since we want the first zero value, as we keeping looping, we'll get to the 0 that is behind us in the array...
{
p = arr + k; // change the value of p
}
}
}   

int main()
{
int nums[6] = { 10, 20, 0, 40, 30, 50 };
int* ptr = nullptr;

findFirstZero(nums, 6, ptr);
if (ptr == nullptr)
{
cout << "The array doesn't have any zeros inside it." << endl;
}
else
{
cout << "The first zero is at address " << ptr << endl;
cout << "It's at index " << ptr - nums << endl;
cout << "The item's value is " << *ptr << " which is zero! I found it." << endl;
}
return( 0 );
}

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