Rotating an array:Segmentation Fault (SIGSEGV) - c++

Question

Given an array of N size. The task is to rotate array by d
elements where d is less than or equal to N.
Constraints: 1 ≤ T ≤ 200 1 ≤ N ≤ 200 1 ≤ A[i] ≤ 1000
Example input:
1
5
1 2 3 4 5
2
Output
3 4 5 1 2
The program I wrote seems legit but when I tried to run it is giving me segment fault. I even ran the above example I'm getting the correct output.
The source is GeeksforGeeks: Rotating and Array.
#include <bits/stdc++.h>
using namespace std;
int main() {
int test_case, numb, from, arr[200];
cin >> test_case;
while (test_case--) {
cin >> numb;
for (int i = 0; i < numb; i++) {
cin >> arr[i];
}
cin >> from;
for (int i = from; i < numb; i++) {
cout << arr[i] << " ";
}
for (int j = 0; j < from; j++) {
cout << arr[j] << " ";
}
cout << "\n";
}
return 0;
}
What are the changes which my code needs? What can I do to avoid such errors in the future?click_to_see_segment_fault

Answer 1

Just submitted your exact code on Rotating an Array | Geek for Geeks (site given in the question) . It works perfectly , and no run time error was encountered .

Answer 2

Run the following input and will see weird results. The problem is when the from is greater than the number of elements itself. Basically you need to do a check to see whether the from itself is more than the number of elements or not numb.
#include <bits/stdc++.h>
using namespace std;
int main() {
int test_case, numb, from, arr[200];
cout<<"\nEnter number of test cases:";
cin >> test_case;
cout<<"Test cases = "<<test_case<<endl;
while (test_case--) {
cout<<"Enter count of elements:";
cin >> numb;
cout<<"Count= "<<numb<<endl;
cout<<"Enter the elements:";
for (int i = 0; i < numb; i++) {
cin >> arr[i];
}
cout<<"Entered elements are :";
for (int i = 0; i < numb; i++) {
cout << arr[i]<<" ";
}
cout<<"\nHow many times to rotated? :";
cin >> from;
cout<<"\nRotate it "<<from<<" times:\n";
for (int i = from; i < numb; i++) {
cout << arr[i] << " ";
}
for (int j = 0; j < from; j++) {
cout << arr[j] << " ";
}
cout << "\n";
}
return 0;
}
Lets provide the input as follows:
Enter number of test cases:1
Test cases = 1
Enter count of elements:1
Count= 1
Enter the elements:2
Entered elements are :2
How many times to rotated? :2
Rotate it 2 times:
2 32666
You see the mistake? The location where 32666 is a problem here. It could crash too in your case.

Answer 3

#include <bits/stdc++.h>
using namespace std;
int main() {
int test_case, numb, from, arr[200];
cout<< "Enter the numbe of test cases"<<endl;
cin >> test_case;
if(test_case > 200)
{
cout<<"Number of test cases above limit";
return 0;
}
while (test_case--) {
cout<<"START TEST CASE"<<test_case<<endl;
cout<<"Enter the number of elements in the array"<<endl;
cin >> numb;
if(numb > 200)
{
cout<<"Array size more than expected skipping testcase"<<endl;
continue;
}
cout<<"Enter the elements of array"<<endl;
for (int i = 0; i < numb; i++) {
cin >> arr[i];
}
cout<<"Enter the number of rotations"<<endl;
cin >> from;
if(from > numb || from < 0)
{
cout <<"rotation index out of range skipping testcase"<<endl;
continue;
}
for (int i = from; i < numb; i++) {
cout << arr[i] << " ";
}
for (int j = 0; j < from; j++) {
cout << arr[j] << " ";
}
cout << "\n";
}
return 0;
}
Extending #Charlie's answer,
The program checks for numbs ranges and from's range.