Kaprekar's Constant Counter
Kaprekar's constant (6174) is useless but fun mathemtatical phenomenon.
The function within the crate you want is
kaprekar::calculate(XXXX) which takes a four-digit number with different integers.
use kaprekar; ... let answer = kaprekar::calculate(1234); // answer == 3 ...
How it Works
- Take any four-digit number where all four digits aren't the same (e.g. 1832 or 9015, not 4444 of 0000)
- Arrange the digits into ascending and descending order (8321 and 1238) and sum
- Repeat the process with the sum (and each successive sum) until it reaces 6174
Applying this process to 6174 will result in 6174.
This function accepts an input of a four-digit, non-repeating number and returns the number of iterations to reach 6174.
If you submit an invalid integer (either repeating or greater than 4 digits) it will return an error.
- Validate the input (AKA a four-digit number with differing integers)
- Instantiate counter variable
And then invoke a recursive function that performs this calculation:
- Convert the integer -> string
- Split string -> vector of characters
- Reorganize vector into two different ones, ascending and descending order, e.g.
- Convert both vectors strings again
- And convert strings back to into integers
- Return the difference of the two integers
- If the answer isn't 6174, increment the counter and run it all again
- Any positive integer is the number of iterations the formula took.
- A return value of -1 means the input was out of bounds
- A return value of 0 means the input itself was 6174.
- Any other positive integer is the number of iterations it took to reach the final result of 6174.