Added solution for 23

1 files changed, 38 insertions, 0 deletions

diff --git a/2023/23/23a.c b/2023/23/23a.c
new file mode 100644
index 0000000..fb6ac7d
--- /dev/null
+++ b/2023/23/23a.c
@@ -0,0 +1,38 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define N 200
+
+bool v[N][N];
+char map[N][N];
+int n, s, t, sol;
+
+int max(int x, int y) { return x > y ? x : y; }
+
+int longpath(int i, int j) {
+        if (i == n-1 && j == t) return 0;
+        if (v[i][j]) return -1;
+
+        char c = map[i][j];
+        int ret = -1;
+        v[i][j] = true;
+        if (c == '.' || c == '>') ret = max(ret, longpath(i, j+1));
+        if (c == '.' || c == 'v') ret = max(ret, longpath(i+1, j));
+        if (c == '.' || c == '<') ret = max(ret, longpath(i, j-1));
+        if (c == '.' || c == '^') ret = max(ret, longpath(i-1, j));
+        v[i][j] = false;
+
+        return ret == -1 ? ret : ret + 1;
+}
+
+int main() {
+        for (n = 1; fgets(map[n], N, stdin) != NULL; n++) ;
+        memset(map[0], '#', n);
+        for (int i = 0; i < n; i++) if (map[1][i] == '.') s = i;
+        for (int i = 0; i < n; i++) if (map[n-1][i] == '.') t = i;
+
+        printf("%d\n", longpath(1, s));
+        return 0;
+}