1 files changed, 83 insertions(+), 13 deletions(-)

M 2023/13.hs.c

@@ 1,25 1,95 @@
-#include <stdio.h>
+#define LIBR_IMPLEMENTATION
+#include <r.h>
 
 #include "input.h"
 
-int main(int argc, char* argv[])
+static int check_reflection_vertical(int n, int c)
 {
-    printf("%s:\n", argv[1]);
+    int X = size[n][0];
+    int Y = size[n][1];
 
-    for(int n = 0; n < N; n++) {
-        printf("%dx%d\n", size[n][0], size[n][1]);
-        for(int y = 0; y < size[n][1]; y++) {
-            for(int x = 0; x < size[n][0]; x++) {
-                if(mirror[n][y][x]) {
-                    printf("#");
-                } else {
-                    printf(".");
-                }
+    for(int y = 0; y < Y; y++) {
+        for(int i = 0; i < X; i++) {
+            int a = c-i;
+            if(a < 0) continue;
+            int b = c+1+i;
+            if(b >= X) continue;
+            /*printf("%d %d: %d %d\n", (a+1), (b+1), mirror[n][y][a], mirror[n][y][b]);*/
+            if(mirror[n][y][a] != mirror[n][y][b]) {
+                return 0;
+            }
+        }
+    }
+
+    return 1;
+}
+
+static int check_reflection_horizontal(int n, int r)
+{
+    int X = size[n][0];
+    int Y = size[n][1];
+
+    for(int x = 0; x < X; x++) {
+        for(int i = 0; i < Y; i++) {
+            int a = r-i;
+            if(a < 0) continue;
+            int b = r+1+i;
+            if(b >= Y) continue;
+            /*printf("%d %d: %d %d\n", (a+1), (b+1), mirror[n][a][x], mirror[n][b][x]);*/
+            if(mirror[n][a][x] != mirror[n][b][x]) {
+                return 0;
+            }
+        }
+    }
+
+    return 1;
+}
+
+static int find_reflection(int n)
+{
+    int X = size[n][0];
+    int Y = size[n][1];
+
+    int v = 0;
+    for(; v < X-1; v++) {
+        if(check_reflection_vertical(n, v)) {
+            return (v+1);
+        }
+    }
+
+    int r = 0;
+    for(; r < Y-1; r++) {
+        if(check_reflection_horizontal(n, r)) {
+            return (r+1)*100;
+        }
+    }
+
+    failwith("unreachable?");
+}
+
+static void draw_pattern(int n)
+{
+    for(int y = 0; y < size[n][1]; y++) {
+        for(int x = 0; x < size[n][0]; x++) {
+            if(mirror[n][y][x]) {
+                printf("#");
+            } else {
+                printf(".");
             }
-            printf("\n");
         }
         printf("\n");
     }
+}
+
+int main(int argc, char* argv[])
+{
+    int sum = 0;
+    for(int n = 0; n < N; n++) {
+        /*draw_pattern(n);*/
+        sum += find_reflection(n);
+    }
+
+    printf("%s: %d\n", argv[1], sum);
 
     return 0;
 }