https://github.com/kaanaktas/luhn-algorithm
Luhn Algorithm implementation with Go
https://github.com/kaanaktas/luhn-algorithm
go golang luhn-algorithm
Last synced: 2 months ago
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Luhn Algorithm implementation with Go
- Host: GitHub
- URL: https://github.com/kaanaktas/luhn-algorithm
- Owner: kaanaktas
- Created: 2019-09-08T22:37:45.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2020-09-06T12:27:02.000Z (over 4 years ago)
- Last Synced: 2025-01-25T05:25:04.904Z (4 months ago)
- Topics: go, golang, luhn-algorithm
- Language: Go
- Homepage:
- Size: 4.88 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Luhn Algorithm
## Setup
- Download and install [Golang](https://golang.org/dl/)
- Download [Visual Studio Code](https://code.visualstudio.com/download) and install [go plugin](https://code.visualstudio.com/docs/languages/go)
- Clone project ```git clone https://github.com/kaanaktas/luhn-algorithm.git``` and run:
```bash
git clone https://github.com/kaanaktas/luhn-algorithm.git
cd luhn-algorithm
go run main.go
```
If you can see ```hello world from awesome golang land``` then run the following command:
```bash
go test .
```
Implement [luhn.IsValid](./luhn.go) method and fix the tests.
Benchmark test ````go test -bench=. .````
## Luhn Algorithm
Given a number determine whether or not it is valid per the Luhn formula.
The [Luhn algorithm](https://en.wikipedia.org/wiki/Luhn_algorithm) is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers.
The task is to check if a given string is valid.
### Validating a Number
Strings of length 1 or less are not valid. Spaces are allowed in the input, but they should be stripped before checking. All other non-digit characters are disallowed.
**Example 1: valid credit card number**
> 4539 1488 0343 6467
The first step of the Luhn algorithm is to double every second digit, starting from the right. We will be doubling
> 4_3_ 1_8_ 0_4_ 6_6_
If doubling the number results in a number greater than 9 then subtract 9 from the product. The results of our doubling:
> 8569 2478 0383 3437
Then sum all of the digits:
> 8+5+6+9+2+4+7+8+0+3+8+3+3+4+3+7 = 80
If the sum is evenly divisible by 10, then the number is valid. This number is valid!
**Example 2: invalid credit card number**
> 8273 1232 7352 0569
Double the second digits, starting from the right
> 7253 2262 5312 0539
Sum the digits
> 7+2+5+3+2+2+6+2+5+3+1+2+0+5+3+9 = 57
*57* is not evenly divisible by *10*, so this number is not valid.