Buffer overrun warning - c++

Question

This script spreads all the digits of a number in an array, so that by doing this: spread(number)[position] you can access the digit with relative position. Now the compilers gives me a Buffer overrun warning (C6386), which I assume is caused by exceeding an array bounds (correct me if I'm wrong), but I scripted the function such that such thing doesn't happen, and the program is still malfunctioning
#include <iostream>
#include <math.h>
using namespace std;
unsigned int size(long long int num)
{
unsigned int size = 1;
while (num >= pow(10, size)) size++;
return size;
}
int* spread(int num)
{
unsigned int digit;
int* nums = new int[size(num)];
for (unsigned int P = 0; P <= size(num) - 1; P++)
{
digit = num - num / 10 * 10;
num /= 10;
nums[P] = digit; //Right in this line the program doesn't seem to behave correctly
}
return nums;
}
int main()
{
cout << split(377)[0] << endl;
cout << split(377)[1] << endl;
cout << split(377)[2] << endl;
system("PAUSE");
return 0x0;
}
/*
Output of the program:
7
7
-842150451 <-- there should be a 3 here
Press any key to continue . . .
*/

Answer 1

The body of your for loop interferes with your end condition:
P=0, num=377, size(num) = 3, P <= 2 = true
P=1, num=37, size(num) = 2, P <= 1 = true
P=2, num=3, size(num) = 1, P <= 0 = false
The fix is to calculate size(num) up front and use that in your loop condition:
int numdigits = size(num);
for (int P=0; P < numdigits; P++) { ... }

Answer 2

{
unsigned int digit;
int* nums = new int[size(num)];
int P = 0;
while(num!=0)
{
digit = num - num / 10 * 10;
num /= 10;
nums[P++] = digit; //Right in this line the program doesn't seem to behave correctly
}
return nums;
}
You will store the digit until the number is 0.
Use this condition and your Code works.
But you have memory leaks...
You have to free dynamic memory!
Update: There is a short code, which works ;-)
#include <iostream>
#include <vector>
#include <string>
using namespace std;
vector<size_t> spread(int const num)
{
string number = to_string(num);
vector<size_t> digits;
for(size_t i = 0; i < number.size(); ++i)
{
digits.push_back(number[i] - '0');
}
return digits;
}
int main()
{
auto vec = spread(12345000);
for (auto elem : vec)
{
cout << elem << endl;
}
system("PAUSE");
return 0x0;
}