Print last digits of an integer gradually? - c++

Question

I am trying to to print the last digits of a user inputted integer.
For example if the user inputs 5432
my output is
2
32
432
5432.
I have managed to write the code for this using a while loop, however i don't understand why my loop does not terminate, please help me terminate it?
void main()
{
//declare variables
int input, output, modulu = 10;
//read input from user
cout << "Please enter a number: ";
cin >> input;
int test = input % modulu; // test checks if all the number has been printed
//disect number
while (test > 0);
{
output = input % modulu;
modulu = modulu * 10;
cout << endl << output << endl;
test = input % modulu;
}
}

Answer 1

test is always > 0 for any input > 0
you can achieve the same with different loop:
int input, modulu = 1;
cout << "Please enter a number: ";
cin >> input;
do {
modulu *= 10;
cout << endl << (input % modulu) << endl;
} while ((input % modulu) != input);

Answer 2

Just
test = input / modulu;
instead of test = input % modulu;

Answer 3

For starters there is a semicolon after the while statement.
while (test > 0);
^^^
So the loop is infinite provided that the last digit of the entered number is not equal to 0.
However if you remove the semicolon the condition is invalid because test == 0 only in the case when the last digit is equal to 0.
Take into acount that main in C++ shall have return type int.
The program can look the following way
#include <iostream>
int main()
{
while ( true )
{
const unsigned int Base = 10;
std::cout << "Please enter a non-negative number (0-exit): ";
unsigned int x;
if ( !( std::cin >> x ) || x == 0 ) break;
unsigned int y = x;
unsigned int modulo = 1;
do
{
modulo *= Base;
std::cout << x % modulo << std::endl;
} while ( y /= Base );
std::cout << std::endl;
}
}
If for example to enter
123456789
0
then the output will look like
Please enter a non-negative number (0-exit): 123456789
9
89
789
6789
56789
456789
3456789
23456789
123456789
Please enter a non-negative number (0-exit): 0

Answer 4

Your first problem is here:
while (test > 0);
The ; terminates the while-statement and the code will stay in the while forever. In other words - all the code below is never executed. Remove the ;
Your second problem is the way you handle test - don't take modulo but divide by 10 instead. Like this:
int main()
{
//declare variables
int input, output, modulu = 10;
//read input from user
cout << "Please enter a number: ";
cin >> input;
int test = input; // <------------- Just make test equal to the input
while (test > 0) // <------------- The ; removed
{
output = input % modulu;
modulu = modulu * 10;
cout << endl << output << endl;
test = test / 10; // <----------- Divide by 10
}
return 0;
}
Notice that the above code has some problems with zeros, e.g. 1001 will output 1 1 1 1001 instead of 1 01 001 1001.
You can fix that by a completely different approach using stringinstead of int
Like:
int main()
{
//declare variables
string input;
//read input from user
cout << "Please enter a number: ";
cin >> input;
cout << input << endl;
int size = input.size();
int tmp = size;
while (tmp >= 0)
{
for (int t = tmp; t < size; t ++) cout << input[t];
cout << endl;
--tmp;
}
return 0;
}