Shifting Array Elements in c++ - c++

Question

Write a program that uses an array of size eight (8) and then prompts
the user to input eight integers for the array. The program should do
the following:
Print the numbers in the output given in the sample Input/Output.
The user is prompted to enter an integer value k, the program will then shift the array elements k positions to the right, while the last
K elements are moved to the beginning of the array. For example: if
we have an array [1 2 3 4 5 6 7 8], shifting 2 positions to the right
should give the array [7 8 1 2 3 4 5 6].
I did this question but I got the output (if assumed number of shift = 3)
[1 0 3 1 2 3 4 5] which is wrong, the output should be [6 7 8 1 2 3 4 5]
This is my code, what is the mistake?
#include<iostream>
using namespace std;
int main()
{
int arrays[8];
int k;
cout<<"Enter Values for a Arrays of size 8"<<endl;
for(int i=0; i<8; i++)
{
cin>>arrays[i];
}
cout<<"You Entered Numbers are: [ ";
for(int i=0; i<8; i++)
{
cout<<arrays[i]<<" ";
}
cout<<" ]\n";
cout<<"Enter the Number of Shift: ";
cin>>k;
for(int i=8; i>0; i--)
{
arrays[i]=arrays[i-k];
}
//The Output
for(int i=0; i<8; i++)
{
cout<<arrays[i]<<" ";
}
return 0;
}

Answer 1

The error is in
for(int i=8; i>0; i--)
{
arrays[i]=arrays[i-k];
}
First of all when i<3 you get a negative index. You can solve this using the % operator which returns the reminder.
Secondly you are overwriting the values that still must be copied. For example suppose the shifting is 3: at the first iteration you copy the fifth element inside the eighth. But then you should also copy the eighth inside the third.
One simple solution is to declare a new array and do the following:
int shifted[8];
...
for (int i=0; i<8; i++)
{
shifted[i] = arrays[(i-k)%8]
}
Consider also using C++ vectors.