things

c/euler.c

@@ -1,4 +1,36 @@
 #include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+typedef struct unsigned_int_sized_array {
+  int size;
+  int allocated_size;
+  unsigned int *elements_ptr;
+} unsigned_int_sized_array;
+
+/* typedef struct unsigned_int_sized_array thing; */
+
+unsigned_int_sized_array unsigned_int_sized_array_init() {
+  unsigned_int_sized_array array;
+  array.size = 0;
+  array.allocated_size = 16;
+  unsigned int * elts = malloc(sizeof(unsigned int) * 16);
+  array.elements_ptr = elts;
+  return array;
+}
+
+void reallocate(unsigned_int_sized_array array) {
+  array.allocated_size *= 2;
+  realloc(array.elements_ptr, sizeof(unsigned int) * array.allocated_size);
+}
+
+void push(unsigned_int_sized_array array, unsigned int new_elt) {
+  if (array.size >= array.allocated_size) {
+    reallocate(array);
+  }
+  array.elements_ptr[array.size] = new_elt;
+  array.size++;
+}
 
 void print_result(int result) {
   printf("%d\n", result);

c/euler003.c

@@ -0,0 +1,35 @@
+#include "euler.h"
+#include "generic_list.h"
+#include <math.h>
+#include <stdbool.h>
+
+bool prime(long int n) {
+  for (long i = 2; i <= sqrt(n); i++) {
+    if (n % i == 0) {
+      return false;
+    }
+  }
+  return true;
+}
+
+generic_list *factors(long n) {
+  static generic_list list;
+  generic_list_init(&list);
+  for (long i = 2; i <= sqrt(n); i++) {
+    if (n % i == 0) {
+      if (prime(i)) {
+        generic_list_add(&list, LONG, &i);
+      }
+    }
+  }
+  return &list;
+}
+
+int main() {
+  generic_list *result;
+
+  result = factors(600851475143);
+  generic_list_print(result);
+
+  return 0;
+}

c/generic_list.c

@@ -0,0 +1,130 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+#include "generic_list.h"
+
+void generic_node_init(generic_node *n, GENERIC_LIST_TYPE type, void* value) {
+  n->data = malloc(sizeof(value));
+  n->type = type;
+  memcpy(n->data, value, sizeof(value));
+}
+
+void generic_list_init(generic_list *l) {
+  l->size = 0;
+  l->head = NULL;
+  l->tail = NULL;
+}
+
+int generic_list_size(generic_list *l) {
+  return l->size;
+}
+
+void generic_list_add(generic_list *l, GENERIC_LIST_TYPE type, void* value) {
+  generic_node *node = malloc(sizeof(generic_node));
+
+  node->data = malloc(sizeof(value));
+  node->type = type;
+  node->next = NULL;
+  memcpy(node->data, value, sizeof(value));
+
+  if (l->size == 0) {
+    l->head = node;
+    l->tail = node;
+  } else {
+    l->tail->next = node;
+    l->tail = node;
+  }
+
+  l->size++;
+}
+
+generic_node generic_list_get(generic_list *l, int index) {
+  assert(index >= l->size);
+  int i = 0;
+  generic_node* current = l->head;
+  while(i < index) {
+    current = current->next;
+    i++;
+  }
+  return *current;
+}
+
+/*
+int generic_list_get(generic_list *l, int index) {
+  if (index >= l->count) {
+    printf("error: index out of range");
+    return 0;
+  }
+
+  return l->data[index];
+}
+
+void generic_list_set(generic_list *l, int index, int value) {
+  if (index >= l->count) {
+    printf("error: index out of range");
+    return;
+  }
+
+  l->data[index] = value;
+}
+
+void generic_list_delete(generic_list *l, int index) {
+  if (index >= l->count) {
+    printf("error: index out of range");
+    return;
+  }
+
+  int j = index;
+  for (int i = index; i < l->count; i++) {
+    l->data[j] = l->data[i];
+    j++;
+  }
+
+  l->count--;
+}
+
+int generic_list_sum(generic_list *l) {
+  int sum = 0;
+  for (int i = 0; i < l->count; i++) {
+    sum += (l->data[i]);
+  }
+  return sum;
+}
+
+*/
+void generic_list_print(generic_list *l) {
+  generic_node *node = l->head;
+  while (node != NULL) {
+    switch(node->type) {
+      case INT:
+        {
+          int value = *(int*)(node->data);
+          printf("%i ", value);
+        }
+        break;
+
+      case LONG:
+        {
+          long value = *(long*)(node->data);
+          printf("%li ", value);
+        }
+        break;
+
+      case LONG_LONG:
+        {
+          long long value = *(long long*)(node->data);
+          printf("%lli ", value);
+        }
+        break;
+    }
+    node = node->next;
+  }
+  printf("\n");
+}
+
+/*
+void generic_list_free(generic_list *l) {
+  free(l->data);
+}
+*/

c/generic_list.h

@@ -0,0 +1,33 @@
+#ifndef GENERIC_LIST_H_
+#define GENERIC_LIST_H_
+
+typedef enum {
+  INT,
+  LONG,
+  LONG_LONG
+} GENERIC_LIST_TYPE;
+
+typedef struct generic_node {
+  void* data;
+  GENERIC_LIST_TYPE type;
+  struct generic_node* next;
+} generic_node;
+
+typedef struct generic_list_ {
+  int size;
+  generic_node *head;
+  generic_node *tail;
+} generic_list;
+
+void generic_node_init(generic_node *n, GENERIC_LIST_TYPE type, void* value);
+void generic_list_init(generic_list *l);
+int generic_list_count(generic_list *l);
+void generic_list_add(generic_list *l, GENERIC_LIST_TYPE type, void* value);
+generic_node generic_list_get(generic_list *l, int index);
+void generic_list_set(generic_list *l, int index, void* value);
+void generic_list_delete(generic_list *l, int index);
+long long generic_list_sum(generic_list *l);
+void generic_list_print(generic_list *l);
+void generic_list_free(generic_list *l);
+
+#endif

crystal/001/euler001.cr

@@ -0,0 +1 @@
+puts (1..999).select { |n| (n % 3 == 0) || (n % 5 == 0) }.sum

crystal/002/euler002.cr

@@ -0,0 +1,18 @@
+def fibonacci_nums_up_to(n)
+  result = [1] of Int32
+
+  a = 1
+  b = 2
+  accum = 0
+
+  while accum < n
+    accum = a + b
+    result << b
+    a = b
+    b = accum
+  end
+
+  result
+end
+
+puts fibonacci_nums_up_to(4000000).select{ |n| n.even? }.sum

crystal/003/euler003.cr

@@ -0,0 +1,26 @@
+#wrong approach, should just do recursive trial division...
+
+def eratosthenes_sieve(n)
+  sieve = Array.new(n + 1, true)
+  sieve[0] = false
+  sieve[1] = false
+
+  2.step(to: Math.sqrt(n)) do |i|
+    if sieve[i]
+      (i * i).step(to: n, by: i) do |j|
+        sieve[j] = false
+      end
+    end
+  end
+
+  result = sieve.map_with_index { |b, i| b ? i : nil }.compact
+end
+
+def prime_factors(n)
+  nums = eratosthenes_sieve(n).select { |i| n % i == 0 }
+  nums = nums + nums.map { |i| n / i }
+end
+
+puts eratosthenes_sieve(600851475143)
+
+puts prime_factors(600851475143).max

haskell/euler060.hs

@@ -0,0 +1,40 @@
+import Data.List (unfoldr)
+import Data.List (find)
+import Data.Maybe (listToMaybe)
+
+minus (x:xs) (y:ys) = case (compare x y) of
+           LT -> x : minus  xs  (y:ys)
+           EQ ->     minus  xs     ys
+           GT ->     minus (x:xs)  ys
+minus  xs     _     = xs
+union (x:xs) (y:ys) = case (compare x y) of
+           LT -> x : union  xs  (y:ys)
+           EQ -> x : union  xs     ys
+           GT -> y : union (x:xs)  ys
+union  xs     []    = xs
+union  []     ys    = ys
+
+primesToQ m = eratos [2..m]
+  where
+    eratos []     = []
+    eratos (p:xs) = p : eratos (xs `minus` [p*p, p*p+p..m])
+
+combinations 0 _ = [[]]
+combinations n xs = [ xs !! i : x | i <- [0..(length xs)-1]
+                                  , x <- combinations (n-1) (drop (i+1) xs) ]
+
+pfactors prs n = unfoldr (\(ds,n) -> listToMaybe
+     [(x, (dropWhile (< x) ds, div n x)) | x <- takeWhile ((<=n).(^2)) ds ++
+                                                   [n|n>1], mod n x==0]) (prs,n)
+
+primes = 2 : 3 : [x | x <- [5,7..], head (pfactors (tail primes) x) == x]
+
+isPrime n = n > 1 &&
+              foldr (\p r -> p*p > n || ((n `rem` p) /= 0 && r))
+                True primes
+
+is_concatenatable_pair list = isPrime (read(show(list!!0) ++ show(list!!1))) && isPrime (read(show(list!!1) ++ show(list!!0)))
+
+is_concatenatable_set list = and (map is_concatenatable_pair (combinations 2 list))
+
+solution = find is_concatenatable_set (combinations 4 (primesToQ 30000))

lisp/euler.lisp

@@ -57,3 +57,19 @@
 (defun max-of (list)
   (reduce #'max list)
 )
+
+(defun eratosthenes-helper (expr list-one list-two)
+  (if (> (length list-one) 0) (eratosthenes-helper expr (filter (partial expr (first list-one)) (rest list-one)) (filter (partial expr (first list-one)) list-two)) list-two)
+)
+
+(defun eratosthenes (n)
+  (eratosthenes-helper (lambda (x a) (and (eq (mod a x) 0) (/= a x))) (range 2 (sqrt n)) (range 2 n))
+)
+
+(defun combinations (count list)
+  (cond
+    ((zerop count) '(())) ; one combination of zero element.
+    ((endp list)   '())   ; no combination from noe element.
+    (t (nconc (mapcar (let ((item (first list))) (lambda (combi) (cons item combi)))
+                      (combinations (1- count) (rest list)))
+              (combinations count (rest list))))))

lisp/euler003.lisp

@@ -1,13 +1,5 @@
 (load "euler.lisp")
 
-(defun eratosthenes-helper (expr list-one list-two)
-  (if (> (length list-one) 0) (eratosthenes-helper expr (filter (partial expr (first list-one)) (rest list-one)) (filter (partial expr (first list-one)) list-two)) list-two)
-)
-
-(defun eratosthenes (n)
-  (eratosthenes-helper (lambda (x a) (and (eq (mod a x) 0) (/= a x))) (range 2 (sqrt n)) (range 2 n))
-)
-
 (defun prime-factors (n)
   (select (lambda (a) (eq (mod n a) 0)) (eratosthenes (sqrt n)))
 )

lisp/euler060.lisp

@@ -0,0 +1,8 @@
+(load "euler.lisp")
+
+(defun set-of-concatenatable-primes (list)
+)
+
+(defun solution ()
+  (combinations 5 (eratosthenes 30000))
+)

ruby/euler.rb

@@ -21,13 +21,7 @@ class Integer
   end
 
   def factorial
-    i = 1
-    n = self
-    while (n > 0)
-      i *= n
-      n -= 1
-    end
-    i
+    (2..self).inject(:*)
   end
 
   def to_digit_list

ruby/euler004.rb

@@ -1,13 +1,7 @@
 require_relative 'euler'
 
 def products_of_three_digits
-  [].tap do |products|
-    (100..999).each do |i|
-      (100..999).each do |j|
-        products << i*j
-      end
-    end
-  end
+  (100..999).to_a.combination(2).map { |p| p.inject(:*) }
 end
 
 def solution

ruby/euler058.rb

@@ -0,0 +1,20 @@
+require 'prime'
+
+def solution
+  diagonal_primes = []
+  diagonal_composites = []
+
+  increment = 2
+  num = 1
+  loop do
+    4.times do
+      num += increment
+      if num.prime?
+        diagonal_primes << num
+      else
+        diagonal_composites << num
+      end
+      return num if (diagonal_primes.count.to_f / diagonal_composites.count.to_f) < 0.1
+    end
+  end
+end

ruby/euler060.rb

@@ -0,0 +1,16 @@
+require_relative 'euler'
+
+def set_of_concatenatable_primes_old?(list)
+  list.combination(2).map { |q, r| (q.to_s + r.to_s).to_i.prime? and (r.to_s + q.to_s).to_i.prime? }.all?
+end
+
+def solution
+  Prime.take(200).combination(3).find { |set| set_of_concatenatable_primes?(set) }
+end
+
+def set_of_concatenatable_primes?(list)
+  list.combination(2).each do |q, r|
+    return false unless (q.to_s + r.to_s).to_i.prime? and (r.to_s + q.to_s).to_i.prime?
+  end
+  true
+end