Problem 21

 1def get_proper_divisors(num)
 2    list = (1..num - 1).to_a
 3    divisors = []
 4    list.map{|n| if num % n == 0 
 5             divisors.push(n)
 6    end}
 7    divisors.reduce(:+)
 8end
 9
10def is_amicable(num)
11    a = get_proper_divisors(num)
12    b = get_proper_divisors(a)
13    if a != b
14        if b == num 
15            true
16        else
17            false
18        end
19    end
20end
21
22amicable = []
23(220..9999).to_a.map{|n| if is_amicable(n) == true 
24                     amicable.push(n)
25end}
26puts amicable.reduce(:+)

 1#include<stdio.h>
 2#include<math.h>
 3#include<stdlib.h>
 4
 5struct pair_am_num{
 6    int a;
 7    int b;
 8    struct pair_am_num * next;
 9};
10
11struct num_exists{
12    int num;
13    struct num_exists * next;
14};
15
16struct pair_am_num * head = NULL;
17struct num_exists * tracker = NULL;
18int d(int num){
19    int sum = 0;
20    printf("%d\n", num);
21    for(int i = 2; i <num; i++){
22        if(num % i == 0){
23            printf("adding %d\n", i);
24            sum += i;
25        }
26    }
27     sum++; //include 1
28     return sum;
29}
30
31void add_to_am_num(int a, int b){
32    if(head == NULL){
33        head = malloc(sizeof(struct pair_am_num));
34        head->a = a;
35        head->b = b;
36        head->next = NULL;
37    }
38    else{
39        struct pair_am_num * temp = head;
40        while(temp->next != NULL){
41            temp = temp->next;
42        }
43        temp->next = malloc(sizeof(struct pair_am_num));
44        temp->next->a = a;
45        temp->next->b = b;
46        temp->next->next = NULL;
47    }
48}
49
50int does_exist(int num){
51    if(tracker == NULL){
52        tracker = malloc(sizeof(struct num_exists));
53        tracker->num = num;
54        tracker->next = NULL;
55        return 0;
56    }
57    else{
58        struct num_exists * temp = tracker;
59        while(temp->next != NULL){
60            if(temp->num == num){
61                return 1;
62            }
63            temp = temp->next;
64        } 
65        temp->next = malloc(sizeof(struct num_exists));
66        temp->next->next = NULL;
67        temp->next->num = num;
68        return 0;
69    }
70}
71
72void get_pairs(){
73    int b;
74    for (int a = 1; a <= 10000; a++){
75        b = d(a);
76        printf("a: %d\n\nComparing %d and %d \n",a, b, d(b));
77        if(d(b) == a && does_exist(a) == 0 && does_exist(b) == 0){
78            add_to_am_num(a, b);
79        }
80    }
81}
82
83int get_sum(){
84    get_pairs();
85    struct pair_am_num * temp = head;
86    int sum = 0;
87    while(temp != NULL){
88        sum = sum + temp->a + temp->b;
89        temp = temp->next;
90    }
91    return sum;
92}
93
94int main(){
95    printf("%d\n\n", get_sum());
96    return 0;
97}