24 lines
911 B
YAML
24 lines
911 B
YAML
|
title: Evaluate the sum of all amicable pairs under 10000.
|
||
|
|
url: http://projecteuler.net/problem=21
|
||
|
|
|
||
|
|
desc: |
|
||
|
|
Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n).
|
||
|
|
If d(a) = b and d(b) = a, where a b, then a and b are an amicable pair and each of a and b are called amicable numbers.
|
||
|
|
For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110; therefore d(220) = 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.
|
||
|
|
Evaluate the sum of all the amicable numbers under 10000.
|
||
|
|
|
||
|
|
solution: Bruteforce
|
||
|
|
|
||
|
|
todo: Implement caching in other solutions
|
||
|
|
|
||
|
|
solutions:
|
||
|
|
solve.php:
|
||
|
|
desc: (Uses a cache to find allready calculated values for d()
|
||
|
|
language: php
|
||
|
|
solve.rb:
|
||
|
|
desc: Basic solution
|
||
|
|
language: ruby
|
||
|
|
solve.c:
|
||
|
|
desc: ANSI C solution (Compiled with TCC)
|
||
|
|
language: c
|