Unable to display a reversed number in C++ - c++

Question

I'm having difficulty printing a reversed number. The algorithm is working as expected for the reversal of the user's input but cannot display correctly:
#include <iostream>
#include <stdio.h>
using namespace std;
int main()
{
int rem, OriValue, InValue2 = 0, InValue = 0;//rem = remainder,InValue = User input
bool neg = false; // Boolean Variable to remember input value
//Request customer to enter a int value
cout << "Enter any decimal integer value >= 0:";
cin >> InValue;
OriValue = InValue;
if(InValue < 0)
{
neg = true;
InValue = -InValue;
cout << "Input value is negative :" << InValue <<"\n";
}
else if (InValue > 0 )
cout << "Input value is positive:"<< InValue <<"\n";
do
{
rem = (InValue % 10);
cout << "Remainder value:"<< rem << "\n";
InValue = InValue / 10;
}
while (InValue != 0);
cout << OriValue << " in reverse is " << InValue << "\n";
// Here is an example of the output:
// -123 in reverse 321
return 0;
}
How can I resolve the problem?

Answer 1

This shoule do the work. Check the comments in the code
#include <iostream>
#include <stdio.h>
using namespace std;
int main()
{
int rem, OriValue, InValue2 = 0, InValue = 0;//rem = remainder,InValue = User input
int reverseVal = 0; // Add this variable to store the reverse number
bool neg = false; // Boolean Variable to remember input value
//Request customer to enter a int value
cout << "Enter any decimal integer value >= 0:";
cin >> InValue;
OriValue = InValue;
if(InValue < 0)
{
neg = true;
InValue = -InValue;
cout << "Input value is negative :" << InValue <<"\n";
}
else if (InValue > 0 )
cout << "Input value is positive:"<< InValue <<"\n";
do
{
rem = (InValue % 10);
cout << "Remainder value:"<< rem << "\n";
InValue = InValue / 10;
// Add this to store
reverseVal = reverseVal*10 + rem;
}
while (InValue != 0);
cout << OriValue << " in reverse is " << reverseVal << "\n";
// Here is an example of the output:
// -123 in reverse 321
return 0;
}

Answer 2

You haven't stored your reversed variable anywhere, and n == 0 is when your loop terminates. When you print n after your loop ends, it has to be 0 as you're seeing. The solution is to store your remainders as you divide down n.
Here are a couple options for achieving this.
Using stringstream:
#include <iostream>
#include <sstream>
using namespace std;
int main() {
int original_value, n;
stringstream ss;
cout << "Enter an integer >= 0:";
cin >> original_value;
n = original_value;
if (n < 0) {
n = -n;
ss << '-';
}
while (n > 0) {
ss << n % 10;
n /= 10;
}
cout << original_value << " in reverse is " << ss.str() << "\n";
return 0;
}
Using reverse:
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
int n = -1234;
string rev = to_string(n);
reverse(rev.begin() + (rev[0] == '-' ? 1 : 0), rev.end());
cout << rev << "\n";
return 0;
}
Sample run:
Enter an integer >= 0: -1234
-1234 in reverse is -4321
If you need an integer at the end, you can always parse it from the string using atoi, istringstream or stoi.