reorganize dir

Signed-off-by: Mia Steinkirch <mia.steinkirch@gmail.com>

other_resources/Project-Euler/021-amicable_numbers.py

@@ -0,0 +1,44 @@
+#!/usr/bin/python3
+# mari von steinkirch @2013
+# steinkirch at gmail
+
+'''
+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.
+'''
+
+def find_sum_proper_divisors(n):
+    sum_proper_div = 0
+    for i in range(1, n):
+        if n%i == 0:
+            sum_proper_div += i
+    return sum_proper_div
+
+
+def amicable_numbers(N):
+    sum_div_list = [find_sum_proper_divisors(i) for i in range(1, N+1)]
+    sum_amicable_numbers = 0
+    set_div = set()    
+    for a in range(1, N):
+        da = sum_div_list[a-1]
+        if da < N:
+            b = da
+            db = sum_div_list[b-1]
+            if a != b and db == a and a not in set_div and b not in set_div:
+                sum_amicable_numbers += a + b
+                set_div.add(a)
+                set_div.add(b)
+    return sum_amicable_numbers
+    
+
+def main():
+    print(amicable_numbers(10000))
+    print('Tests Passed!')
+                   
+if __name__ == '__main__':
+    main()
+