C solution for week 103, part 2

2 files changed, 143 insertions, 0 deletions

diff --git a/challenge-103/abigail/README.md b/challenge-103/abigail/README.md
index 4059ddea7e..9d90314025 100644
--- a/challenge-103/abigail/README.md
+++ b/challenge-103/abigail/README.md
@@ -124,6 +124,7 @@ Output:
 
 ### Solutions
 * [GNU AWK](awk/ch-2.awk)
+* [C](c/ch-2.c)
 * [Lua](lua/ch-2.lua)
 * [Perl](perl/ch-2.pl)
 * [Python](python/ch-2.py)
diff --git a/challenge-103/abigail/c/ch-2.c b/challenge-103/abigail/c/ch-2.c
new file mode 100644
index 0000000000..f776892e0c
--- /dev/null
+++ b/challenge-103/abigail/c/ch-2.c
@@ -0,0 +1,142 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+# include <unistd.h>
+
+/*
+ * See ../README.md
+ */
+
+/*
+ * Run as: cc -o ch-2.o ch-2.c; ./ch-2.o < input-file
+ */
+
+/*
+ * Return a malloced string of the given size, or die with
+ * an error message if it fails.
+ */
+char * malloc_char (size_t size) {
+    char * string = (char *) malloc (size * sizeof (char));
+    if (string == NULL) {
+        perror (NULL);
+        exit (1);
+    }
+    return (string);
+}
+
+int main (void) {
+    char *  line = NULL;
+    size_t  len  = 0;
+    size_t  str_len;
+    struct  track {
+        long long run_time;
+        char *    title;
+    };
+
+    while ((str_len = getline (&line, &len, stdin)) != -1) {
+        long long start_time;
+        long long current_time;
+        long long time_diff;
+        char * file_name = malloc_char (str_len);
+        size_t index;
+        /*
+         * Parse input
+         */
+        if (sscanf (line, "%lld %lld %s",
+                           &start_time, &current_time, file_name) != 3) {
+            fprintf (stderr, "Failed to parse input\n");
+            exit (1);
+        }
+
+        /*
+         * Switch to milliseconds
+         */
+        time_diff = (current_time - start_time) * 1000;
+
+        /*
+         * Open the file, and count the number of lines. Then seek back.
+         */
+        FILE * media_file = fopen (file_name, "r");
+        char ch;
+        size_t number_of_tracks = 0;
+        while ((ch = fgetc (media_file)) != EOF) {
+            if (ch == '\n') {
+                number_of_tracks ++;
+            }
+        }
+
+        if (fseek (media_file, 0, SEEK_SET) == -1) {
+            perror ("Fseek failed");
+            exit (1);
+        }
+
+        /*
+         * Allocate memory for the track info.
+         */
+        struct track * tracks = (struct track *)
+                      malloc (number_of_tracks * sizeof (struct track));
+
+        if (tracks == NULL) {
+            perror ("Mallocing tracks failed");
+            exit (1);
+        }
+
+        /*
+         * Read the file, line by line, and store it on tracks.
+         */
+        char * mline = NULL;
+        size_t mlen = 0;
+        size_t slen = 0;
+        size_t i    = 0;
+        long long total_time = 0;
+        while ((slen = getline (&mline, &mlen, media_file)) != -1) {
+            long long run_time = atoll (mline);
+            char * title = malloc_char (slen);
+            strncpy (title, mline, slen);
+            while (* title != ',') {
+                title ++;
+            }
+            title ++;
+            struct track this_track = {run_time, title};
+            tracks [i ++] = this_track;
+
+            total_time += run_time;
+        }
+
+        /*
+         * Skip complete loops.
+         */
+        time_diff %= total_time;
+
+        /*
+         * Find the right track.
+         */
+        for (size_t i = 0; i < number_of_tracks; i ++) {
+            struct track this_track = tracks [i];
+            if (time_diff - this_track . run_time < 0) {
+                printf ("%s", this_track . title);
+                /*
+                 * C uses integer division, which is quite handy here.
+                 */
+                time_diff  /= 1000;
+                int hours   =  time_diff / 3600;
+                int minutes = (time_diff % 3600) / 60;
+                int seconds =  time_diff         % 60;
+                if (hours > 0) {
+                    printf ("%02d:%02d:%02d\n", hours, minutes, seconds);
+                }
+                else {
+                    printf (     "%02d:%02d\n",        minutes, seconds);
+                }
+                break;
+            }
+            else {
+                time_diff -= this_track . run_time;
+            }
+        }
+
+    }
+    free (line);
+
+    return (0);
+}