rename repo, subdir for yearly challenges

2020/day13/ex1-c.c

@@ -0,0 +1,48 @@
+/* ex1-c: Advent2020 game, day 13/game 1
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define ABS(i)	((i)>=0?(i):(-i))
+
+int main(ac, av)
+    int ac;
+    char **av;
+{
+    struct bus {
+        unsigned bus;
+        unsigned idx;
+    } buses[1024];
+    int len=0, i=0, bus, val, found=0, thebus=0;
+
+    char line[1024], *ptr=line;
+    unsigned long long target;
+
+    target=atol(fgets(line, sizeof line, stdin));
+    fgets(line, sizeof line, stdin);
+    ptr=strtok(line, ",");
+
+    do {
+        if (*ptr != 'x') {
+            buses[len].bus=atol(ptr);
+            buses[len].idx=i;
+            len++;
+        }
+        i++;
+        ptr=strtok(NULL, ",");
+    } while (ptr);
+
+    for (i=0; i<len; ++i) {
+        bus=buses[i].bus;
+        val=((target/bus)+1)*bus;
+        if (found == 0 || val < found) {
+            found=val;
+            thebus=bus;
+        }
+    }
+
+    printf("%s : res=%llu\n", *av, (found-target)*thebus);
+    exit (0);
+}