# Palindrome Products in C

#### Detect palindrome products in a given range.

1 | ```
exercism fetch c palindrome-products
``` |

# Palindrome Products

Detect palindrome products in a given range.

A palindromic number is a number that remains the same when its digits are
reversed. For example, `121`

is a palindromic number but `112`

is not.

Given the definition of a palindromic number, we define a palindrome *product*
to be the product `c`

, such that `a * b = c`

, where `c`

is a palindromic number and
`a`

and `b`

are integers (possibly, but *not* necessarily palindromic numbers).

For example, the palindromic number 9009 can be written as the palindrome
product: `91 * 99 = 9009`

.

It's possible (and indeed common) for a palindrome product to be the product
of multiple combinations of numbers. For example, the palindrome product `9`

has
the factors `(1, 9)`

and `(3, 3)`

.

Write a program that given a range of integers, returns the smallest and largest palindromic product of factors within that range, along with all the factors in the range for that product.

## Example 1

Given the range `[1, 9]`

(both inclusive)...

And given the list of all possible products within this range:
`[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 15, 21, 24, 27, 20, 28, 32, 36, 25, 30, 35, 40, 45, 42, 48, 54, 49, 56, 63, 64, 72, 81]`

The palindrome products are all single digit numbers (in this case):
`[1, 2, 3, 4, 5, 6, 7, 8, 9]`

The smallest palindrome product is `1`

. Its factors are `(1, 1)`

.
The largest palindrome product is `9`

. Its factors are `(1, 9)`

and `(3, 3)`

.

## Example 2

Given the range `[10, 99]`

(both inclusive)...

The smallest palindrome product is `121`

. Its factors are `(11, 11)`

.
The largest palindrome product is `9009`

. Its factors are `(91, 99)`

.

## Getting Started

Make sure you have read the C page on the Exercism site. This covers the basic information on setting up the development environment expected by the exercises.

## Passing the Tests

Get the first test compiling, linking and passing by following the three rules of test-driven development.

The included makefile can be used to create and run the tests using the `test`

task.

1 |
```
make test
``` |

Create just the functions you need to satisfy any compiler errors and get the test to fail. Then write just enough code to get the test to pass. Once you've done that, move onto the next test.

As you progress through the tests, take the time to refactor your implementation for readability and expressiveness and then go on to the next test.

Try to use standard C99 facilities in preference to writing your own low-level algorithms or facilities by hand.

## Source

Problem 4 at Project Euler http://projecteuler.net/problem=4

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.