Merge pull request #4986 from Abigail/abigail/week-133

Abigail/week 133

5 files changed, 94 insertions, 4 deletions

diff --git a/challenge-133/abigail/README.md b/challenge-133/abigail/README.md
index aa835b7f1e..d51d3d73e2 100644
--- a/challenge-133/abigail/README.md
+++ b/challenge-133/abigail/README.md
@@ -6,4 +6,5 @@
 
 ## Part 2
 
+* [C](c/ch-2.c)
 * [Perl](perl/ch-2.pl)
diff --git a/challenge-133/abigail/blog.txt b/challenge-133/abigail/blog.txt
new file mode 100644
index 0000000000..db2d358210
--- /dev/null
+++ b/challenge-133/abigail/blog.txt
@@ -0,0 +1 @@
+https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-133-1.html
diff --git a/challenge-133/abigail/blog1.txt b/challenge-133/abigail/blog1.txt
new file mode 100644
index 0000000000..d67cf83760
--- /dev/null
+++ b/challenge-133/abigail/blog1.txt
@@ -0,0 +1 @@
+https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-133-2.html
diff --git a/challenge-133/abigail/c/ch-2.c b/challenge-133/abigail/c/ch-2.c
new file mode 100644
index 0000000000..fa066f94c9
--- /dev/null
+++ b/challenge-133/abigail/c/ch-2.c
@@ -0,0 +1,88 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+
+/*
+ * Run as: cc -o ch-2.o ch-2.c; ./ch-2.o
+ */
+
+/*
+ * The first 10 Smith numbers are all than 1000, so they will
+ * have at most one prime factor which exceeds 31. They also will
+ * have at most 9 prime factors, as 2^10 > 1000.
+ */
+short small_primes [] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31};
+# define SMALL_PRIMES_SIZE 11
+# define MAX_FACTORS        9
+
+/*
+ * The number of Smith numbers we are after. If you increase this, you
+ * may have to update the values above.
+ */
+# define COUNT             10
+# define BASE              10
+
+/*
+ * Factorize a number, given a set of small primes. This will work
+ * for numbers up to, but not including, p^2, where p is the smallest
+ * prime not included in the set. For the given set, the smallest number
+ * which fails to factorize is 37^2 == 1369.
+ */
+size_t factorize (short n, short * factors) {
+    size_t f_i = 0;   /* Index in output structure */
+    
+    for (size_t i = 0; i < SMALL_PRIMES_SIZE && n > 1; i ++) {
+        short prime = small_primes [i];
+        while (n % prime == 0) {
+            factors [f_i ++] = prime;
+            n /= prime;
+        }
+    }
+    /*
+     * Possible left over large prime
+     */
+    if (n > 1) {
+        factors [f_i ++] = n;
+    }
+
+    return (f_i);
+}
+
+/*
+ * Return the sum of the digits of all the numbers in the array 'numbers'.
+ * We do this by taking each number, and repeatedly modding and dividing 
+ * each by 10.
+ */
+short digitsum (size_t n, short * numbers) {
+    short out = 0;
+    char * tmp;
+    for (size_t i = 0; i < n; i ++) {
+        short number = numbers [i];
+        while (number) {
+            out    += number % BASE;
+            number /= BASE;
+        }
+    }
+    return (out);
+}
+
+
+int main () {
+    short * factors;
+    if ((factors = (short *) malloc (MAX_FACTORS * sizeof (short))) == NULL) {
+        perror ("Malloc failed");
+        exit (1);
+    }
+
+    size_t c = 0;
+    short  n = 0;
+
+    while (c < COUNT) {
+        size_t fc = factorize (++ n, factors);
+        if (fc > 1 && digitsum (1, &n) == digitsum (fc, factors)) {
+            printf ("%d\n", n);
+            c ++;
+        }
+    }
+    free (factors);
+}
diff --git a/challenge-133/abigail/perl/ch-2.pl b/challenge-133/abigail/perl/ch-2.pl
index 178c362ab3..506e4ca1e6 100644
--- a/challenge-133/abigail/perl/ch-2.pl
+++ b/challenge-133/abigail/perl/ch-2.pl
@@ -27,12 +27,11 @@ my $COUNT = 10;
 #
 # Return the sum of the digits of the set of given numbers.
 #
-sub digitsum (@n) {sum map {split //} @n}
+sub digitsum (@n) {sum "@n" =~ /\d/ag}
 
 my $c = 0;
-my $n = 1;
+my $n = 0;
 do {
-    my @factors = factor $n;
+    my @factors = factor ++ $n;
     $c ++, say $n if @factors > 1 && digitsum ($n) == digitsum @factors;
-    $n ++;
 } until $c == $COUNT;