Question

Basically, I have an array given of “x” numbers and I have to output the amount of how many times the sign changed in the numbers of the array.

For example array is:
2 -4 5 6 7 -2 5 -7

The output should be 5. Why? Because the sign changes first time at -4, second time at 5, third time at -2, fourth time at 5 and last time at -7. Total 5 times.

So, I have this so far but that doesn’t work perfectly:

#include <iostream>
using namespace std;

int main()
{
int a[50],n,cs=0,ha=0;



cin >> n;
for (int i=0;i<n;i++)
{
    cin >> a[i];
}
for (int j=1;j<=n;j++)
{
    if(a[j]<0 && a[j-1]>0)
    cs++;
    else if(a[j]>0 && a[j-1]<0)
    cs++;
}
cout << cs << endl;
return 0;
}

Please help!

Answer 1

Your problem is that you’re running into uninitialized memory, which is causing undefined behaviour. You initialize a[0] through a[n-1] in your input loop and then read from a[0] (with j=1 and a[j-1]) to a[n] (j=n and a[j]) in your calculation loop.

Simply change it to j < n.