C solution for week 106, part 2

3 files changed, 106 insertions, 0 deletions

diff --git a/challenge-106/abigail/README.md b/challenge-106/abigail/README.md
index 6c1a682ffc..2f760b9b2e 100644
--- a/challenge-106/abigail/README.md
+++ b/challenge-106/abigail/README.md
@@ -94,6 +94,7 @@ Wikipedia](https://en.wikipedia.org/wiki/Repeating_decimal).
 ### Solutions
 * [AWK](perl/ch-2.awk)
 * [Bash](bash/ch-2.sh)
+* [C](c/ch-2.c)
 * [Perl](perl/ch-2.pl)
 
 ### Blog
diff --git a/challenge-106/abigail/c/ch-2.c b/challenge-106/abigail/c/ch-2.c
new file mode 100644
index 0000000000..2bff0e1281
--- /dev/null
+++ b/challenge-106/abigail/c/ch-2.c
@@ -0,0 +1,102 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+# include <math.h>
+
+/*
+ * See ../README.md
+ */
+
+/*
+ * Run as: cc -o ch-2.o ch-2.c; ./ch-2.o < input-file
+ */
+
+# define BASE 10
+typedef int number;
+
+/*
+ * Perform long division. See ../README.md for details.
+ */
+
+char * long_division (int numerator, int denominator) {
+    /*
+     * Calculate the maximum size of the result
+     */
+    size_t fraction_len =
+       (numerator < denominator ? 1 :
+        floor (log10 (numerator / denominator))) +  // Digits before decimal dot
+                                               1 +  // Decimal dot
+                                  denominator    +  // Digits after decimal dot
+                                               2 +  // Parens
+                                               1;   // Trailing NUL byte
+    /*
+     * Allocate a string to hold the caption.
+     */
+    char * fraction;
+    if ((fraction = (char *) malloc (fraction_len * (sizeof (char)))) == NULL) {
+        perror ("Mallocing string failed");
+        exit (1);
+    }
+
+    /*
+     * Add the first part of the result (upto, and including the dot)
+     */
+    int position;
+    snprintf (fraction, fraction_len, "%d.%n",
+                        numerator / denominator, &position);
+
+    /*
+     * Allocate memory to remember which numerators we have seen;
+     * initialize the entries to 0.
+     */
+    number * seen;
+    if ((seen = (number *) malloc (denominator * (sizeof (number)))) == NULL) {
+        perror ("Mallocing seen structure failed");
+        exit (1);
+    }
+    for (number i = 0; i < denominator; i ++) {
+        seen [i] = 0;
+    }
+
+    /*
+     * We already have the part before the decimal dot; for the part
+     * behind it, we need numerator < denominator
+     */
+    numerator %= denominator;
+
+    while (!seen [numerator]) {
+        if (!numerator) {
+            fraction [position] = '\0';
+            return (fraction);
+        }
+        seen [numerator] = position;
+        fraction [position] = BASE * numerator / denominator + '0';
+        numerator           = BASE * numerator % denominator;
+        position ++;
+    }
+
+    /*
+     * We now have to place the parens -- which means shifting
+     * part of the string created so far.
+     */
+    fraction [position + 2] = '\0';
+    fraction [position + 1] = ')';
+    for (int i = position; i > seen [numerator]; i --) {
+        fraction [i] = fraction [i - 1];
+    }
+    fraction [seen [numerator]] = '(';
+    return (fraction);
+}
+
+
+
+int main (void) {
+    number numerator, denominator;
+    while (scanf ("%d %d", &numerator, &denominator) == 2) {
+        char * fraction = long_division (numerator, denominator);
+        printf ("%s\n", fraction);
+        free (fraction);
+    }
+
+    return (0);
+}
diff --git a/challenge-106/abigail/t/ctest.ini b/challenge-106/abigail/t/ctest.ini
index 91aa95b6cb..247492708c 100644
--- a/challenge-106/abigail/t/ctest.ini
+++ b/challenge-106/abigail/t/ctest.ini
@@ -11,3 +11,6 @@
 2-4  =  Unit fractions

 2-5  =  Dyadic fractions

 2-6  =  Prime fractions

+

+[2-5/c]

+skip =  Requires too much memory