How to handle floatingbpoint exception? - c++

Question

I was creating a code for rotation of specif number in a string and initially i created it for one user input ! It worked as soon as i added on logic for multiple test case its is showing floating point exception.....
can anyone tell me in the code what caused that error !
#include<iostream>
#include<cstring>
using namespace std;
void stringrot(char str[],int n)
{
int l=strlen(str);
char temp[100];
int k=n%l;
for(int i=0;i<k;i++)
{
temp[i]=str[(l-k+i)];
}
for(int i=0;i<l-k;i++)
{
temp[k+i]=str[i];
}
temp[l]='\0';
cout<<temp;
}
int main()
{
int test;
cin>>test;
while(--test>=0)
{
char str[100];
cin.getline(str,50);
int n;
cin>>n;
stringrot(str,n);
}
}
Here is the code !

Answer 1

Let's take a closer look at the while loop in main
while(--test>=0)
{
char str[100];
cin.getline(str,50);
int n;
cin>>n;
stringrot(str,n);
}
Loop Iteration 1
cin.getline(str,50); << reads a line
cin>>n; << reads an integer. After enter is pressed. Enter
is not an integer. Enter is not read and stays
in the stream
stringrot(str,n);
Loop Iteration 2
cin.getline(str,50); << reads a line. Fortunately there is an enter
still in the stream making it really easy to
find the end of the line. It's the first
character that's going to be read.
cin>>n; << reads an integer. Unfortunately the user
probably thinks they are typing in the string
and doesn't type in a number. Oops.
stringrot(str,n);
Anyway stringrot gets called with stringrot("",0), so the first few lines of stringrot wind up looking like
int l=strlen(""); << l will be zero because the string is emtpy
char temp[100];
int k=n%l; << resolves to 0%0 and an integer divided by zero is BOOM!
Solution:
Change the guts of the while loop to something like
char str[100];
cin.getline(str,50);
int n;
cin>>n;
// discard everything else on the line including the end of line character
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
stringrot(str,n);
Why an integer division results in a floating point error, one that isn't a catchable C++ exception by the way, seems to be mostly historical. More here: Why is this a floating point exception?
Recommendation:
Use std::string not char arrays.

Answer 2

#include<iostream>
#include<cstring>
using namespace std;
//void stringrot(char str[],int n)
void stringrot(string str,int n)
{
//int l=strlen(str);
int l=str.size();
char temp[100];
int k=n%l;
for(int i=0;i<k;i++)
{
temp[i]=str[(l-k+i)];
}
for(int i=0;i<l-k;i++)
{
temp[k+i]=str[i];
}
temp[l]='\0';
cout<<temp;
}
int main()
{
int test;
cin>>test;
while(--test>=0)
{
//char str[100];
//cin.getline(str,50);
string str;
cin>>str;
int n;
cin>>n;
stringrot(str,n);
}
}