C solution for week 128, part 2

2 files changed, 107 insertions, 0 deletions

diff --git a/challenge-128/abigail/README.md b/challenge-128/abigail/README.md
index 034d2135be..eb32303239 100644
--- a/challenge-128/abigail/README.md
+++ b/challenge-128/abigail/README.md
@@ -66,6 +66,7 @@ station, so we need minimum 3 platforms.
 
 ### Solutions
 * [AWK](awk/ch-2.awk)
+* [C](awk/ch-2.c)
 * [Perl](perl/ch-2.pl)
 
 ### Blog
diff --git a/challenge-128/abigail/c/ch-2.c b/challenge-128/abigail/c/ch-2.c
new file mode 100644
index 0000000000..260fb60332
--- /dev/null
+++ b/challenge-128/abigail/c/ch-2.c
@@ -0,0 +1,106 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+
+/*
+ * See ../README.md
+ */
+
+/*
+ * Run as: cc -o ch-2.o ch-2.c; ./ch-2.o < input-file
+ */
+# define MINUTES_PER_DAY 24 * 60
+
+int main (void) {
+    char *  arrival_line   = NULL;
+    char *  departure_line = NULL;
+    size_t  a_len          = 0;
+    size_t  d_len          = 0;
+    size_t  a_str_len;
+    size_t  d_str_len;
+
+    if ((a_str_len = getline (&arrival_line, &a_len, stdin)) == -1) {
+        perror ("Failed to read arrival line");
+        exit (1);
+    }
+    if ((d_str_len = getline (&departure_line, &d_len, stdin)) == -1) {
+        perror ("Failed to read departurerrival line");
+        exit (1);
+    }
+
+    /*
+     * Turn any non-digits into spaces.
+     */ 
+    char * line_ptr = arrival_line;
+    while (* line_ptr) {
+        if (* line_ptr < '0' || * line_ptr > '9') {
+            * line_ptr = ' ';
+        }
+        line_ptr ++;
+    }
+
+    line_ptr = departure_line;
+    while (* line_ptr) {
+        if (* line_ptr < '0' || * line_ptr > '9') {
+            * line_ptr = ' ';
+        }
+        line_ptr ++;
+    }
+
+    /*
+     * Initialize the trains array: a counter for every minute in a day
+     */
+    unsigned int trains [MINUTES_PER_DAY];
+    for (size_t i = 0; i < MINUTES_PER_DAY; i ++) {
+        trains [i] = 0;
+    }
+
+    /*
+     * Scan over the arrival/departure times
+     */
+    int a_hour, a_minute, d_hour, d_minute;
+    int a_skip = 0;
+    int d_skip = 0;
+    char * a_ptr = arrival_line;
+    char * d_ptr = departure_line;
+    while (sscanf (a_ptr, "%d %d%n", &a_hour, &a_minute, &a_skip) == 2 &&
+           sscanf (d_ptr, "%d %d%n", &d_hour, &d_minute, &d_skip) == 2) {
+        int arrival   = a_hour * 60 + a_minute;
+        int departure = d_hour * 60 + d_minute;
+        a_ptr += a_skip;
+        d_ptr += d_skip;
+
+        /*
+         * Count the number of trains there are in the station for each
+         * minute of the day
+         */
+        for (int i = arrival; i <= departure; i ++) {
+            trains [i] ++;
+        }
+        if (departure < arrival) {
+            for (int i = 0; i <= departure; i ++) {
+                trains [i] ++;
+            }
+            for (int i = arrival; i < MINUTES_PER_DAY; i ++) {
+                trains [i] ++;
+            }
+        }
+    }
+
+    /*
+     * Find the maximum number of trains
+     */
+    int max = 0;
+    for (int i = 0; i < MINUTES_PER_DAY; i ++) {
+        if (max < trains [i]) {
+            max = trains [i];
+        }
+    }
+
+    printf ("%d\n", max);
+
+    free (arrival_line);
+    free (departure_line);
+
+    return (0);
+}