How do you reverse a 5 digit number in c plus plus?

Answer 1

It really does not matter how many digits there are, the principal is exactly the same. The following function is the most efficient way to reverse any whole number in the range -2,147,483,648 to 2,147,483,647, inclusive (assuming a 32-bit integer). To increase the range, create separate functions to cater for 64-bit and 128-bit integers. Converting the number to a string and reversing the string is also an option (see previous answer, below), however it is by far the least efficient method of reversing a whole number.

int RevNum( int num )

{

const int base = 10;

int remain = 0;

int result = 0;

do

{

remain = num % base;

result *= base;

result += remain;

} while( num /= base);

return( result );

}

Previous Answer

This is assuming the number is decimal.

There are several approaches to the problem, depending on the resources you have available or wish to use to solve it.

One way to achieve this is to isolate the digits through modulo division and the remultiply them in the desired order:

rev = ((original % 10) * 10000) + (((original / 10) % 10) * 1000) + (((original / 100) % 10) * 100) + (((original / 1000) % 10) * 10) + (original / 10000);

An alternative that doesn't look so messy:

int temp = original;

int rev = 0;

for (int i=0;i<5;i++)

{

rev = (rev * 10) + (temp % 10);

temp /= 10;

}

If you're employing strings, then another novel way can be used.

#include

#include

#include

char numstring[6];

snprintf(numstring,5,"%d",original);

strrev(numstring);

rev = atoi(numstring);

Note that these are just examples of how it can be achieved. There is no standard function to reverse a decimal number in C or C++, so it's up to you to find or code a solution for yourself.

Answer 2

It doesn't matter how many digits are involved, the principal is the same.

int RevNum( int num )

{

const int base = 10;

int result = 0;

int remain = 0;

do

{

remain = num % base;

result *= base;

result += remain;

} while( num /= base);

return( result );

}