1 files changed, 76 insertions, 0 deletions

diff --git a/2023/10/10a.c b/2023/10/10a.c
new file mode 100644
index 0000000..d25b0c8
--- /dev/null
+++ b/2023/10/10a.c
@@ -0,0 +1,76 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define N 1000
+
+typedef enum { EAST, SOUTH, WEST, NORTH } direction_t;
+
+int main() {
+        char map[N][N];
+        int i, j, k, n, s;
+        direction_t dir;
+
+        for (n = 0; fgets(map[n], N, stdin) != NULL; n++) ;
+
+        for (i = 0; i < n; i++)
+                for (j = 0; map[i][j]; j++)
+                        if (map[i][j] == 'S')
+                                goto found_s;
+
+found_s:
+        if (map[i][j+1] ==  '7' || map[i][j+1] == '-' || map[i][j+1] == 'J') {
+                j++;
+                dir = EAST;
+                goto found_direction;
+        }
+        if (map[i+1][j] ==  'L' || map[i+1][j] == '|' || map[i+1][j] == 'J') {
+                i++;
+                dir = SOUTH;
+                goto found_direction;
+        }
+        if (j > 0 && (map[i][j-1] ==  'L' || map[i][j-1] == '-' || map[i][j-1] == 'F')) {
+                j--;
+                dir = WEST;
+                goto found_direction;
+        }
+
+found_direction:
+        for (k = 1; map[i][j] != 'S'; k++) {
+                switch (map[i][j]) {
+                case '|':
+                        if (dir == SOUTH) i++;
+                        if (dir == NORTH) i--;
+                        break;
+                case '-':
+                        if (dir == EAST) j++;
+                        if (dir == WEST) j--;
+                        break;
+                case '7':
+                        if (dir == EAST) { i++; dir = SOUTH; }
+                        if (dir == NORTH) { j--; dir = WEST; }
+                        break;
+                case 'F':
+                        if (dir == WEST) { i++; dir = SOUTH; }
+                        if (dir == NORTH) { j++; dir = EAST; }
+                        break;
+                case 'J':
+                        if (dir == EAST) { i--; dir = NORTH; }
+                        if (dir == SOUTH) { j--; dir = WEST; }
+                        break;
+                case 'L':
+                        if (dir == WEST) { i--; dir = NORTH; }
+                        if (dir == SOUTH) { j++; dir = EAST; }
+                        break;
+                default:
+                        printf("Error: dead path\n");
+                        return 1;
+                }
+        }
+
+        s = (k+1)/2;
+
+        printf("%d\n", s);
+        return 0;
+}