rename repo, subdir for yearly challenges

2020/day03/ex2-c.c

@@ -0,0 +1,56 @@
+/* ex1-c: Advent2020 game, day 3/game 2
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+struct {
+    int dx;
+    int dy;
+    int pos;
+    int count;
+} set[] = {
+    { 1,  1, 0, 0},
+    { 3,  1, 0, 0},
+    { 5,  1, 0, 0},
+    { 7,  1, 0, 0},
+    { 1,  2, 0, 0},
+    {-1, -1, 0, 0}              /* end marker - not necessary */
+};
+
+int my_strlen(str)
+    char *str;
+{
+    int i;
+    for (i=0; *str; ++i, ++str)
+        ;
+    return i;
+}
+
+int main(ac, av)
+    int ac;
+    char **av;
+{
+    int line=1, linelen=0, mod=0, i;
+    unsigned long res=1;
+    char str[80];
+
+    scanf("%s", str);          /* ignore 1st line */
+
+    while (scanf("%s", str) != EOF) {
+        line++;
+        linelen=my_strlen(str);
+        for (i=0; set[i].dx >= 0; ++i) {
+            if (! (line % set[i].dy )) { /* line ok for this set */
+                set[i].pos += set[i].dx; /* increment set column */
+                mod = set[i].pos % linelen;
+                if ( str[mod] == '#')
+                    set[i].count++;
+            }
+        }
+    }
+    for (i=0; set[i].dx != -1; ++i)
+        res*=set[i].count;
+    printf ("%s : lines=%d res=%lu\n", *av, line, res);
+    exit (0);
+}