From f6b142d0d5332b2bd308cc37da93c860be595653 Mon Sep 17 00:00:00 2001
From: Parker Macdonald <parker_macdonald@mines.edu>
Date: Sun, 8 Dec 2024 01:35:44 -0700
Subject: [PATCH] day 8 part 1

---
 day_8/1.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 day_8/1.c

diff --git a/day_8/1.c b/day_8/1.c
new file mode 100644
index 0000000..34c4d03
--- /dev/null
+++ b/day_8/1.c
@@ -0,0 +1,91 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define GRID_SIZE 50
+
+typedef struct point {
+  int x, y;
+} point_t;
+
+typedef struct lots_of_points {
+  point_t points[4];
+  unsigned char index;
+} lots_of_points_t;
+
+int main(void) {
+  FILE *fp = fopen("input", "r");
+
+  if (fp == NULL) {
+    perror("input");
+    return 1;
+  }
+
+  char antinodes[GRID_SIZE][GRID_SIZE] = {0};
+
+  lots_of_points_t data['z' + 1] = {0};
+
+  for (unsigned int i = 0; i < GRID_SIZE; i++) {
+    unsigned char buffer[GRID_SIZE] = {0};
+    size_t read = fread(&buffer, sizeof(char), GRID_SIZE, fp);
+
+    if (read == 0) {
+      fprintf(stderr, "oopsy daisy\n");
+      fclose(fp);
+      return 1;
+    }
+
+    // move past the newline
+    fseek(fp, 1, SEEK_CUR);
+
+    for (unsigned int j = 0; j < GRID_SIZE; j++) {
+      const unsigned char freq = buffer[j];
+      if (freq != '.') {
+        const point_t point = {(int)j, (int)i};
+        data[freq].points[data[freq].index] = point;
+        data[freq].index++;
+      }
+    }
+  }
+
+  unsigned int sum = 0;
+  for (unsigned int i = 0; i < 'z' + 1; i++) {
+    if (data[i].index == 0) {
+      continue;
+    }
+
+    for (unsigned int j = 0; j < data[i].index; j++) {
+      const point_t point = data[i].points[j];
+      for (unsigned int k = 0; k < data[i].index; k++) {
+        if (j == k) {
+          continue;
+        }
+
+        const point_t other_point = data[i].points[k];
+
+        const int dist_x = point.x - other_point.x;
+        const int dist_y = point.y - other_point.y;
+
+        const point_t antinode = {point.x + dist_x, point.y + dist_y};
+
+        if (antinode.x >= GRID_SIZE || antinode.x < 0 ||
+            antinode.y >= GRID_SIZE || antinode.y < 0) {
+          continue;
+        }
+
+        if (antinodes[antinode.y][antinode.x] == 1) {
+          continue;
+        }
+
+        antinodes[antinode.y][antinode.x] = 1;
+
+        sum++;
+      }
+    }
+  }
+
+  printf("%u\n", sum);
+
+  fclose(fp);
+
+  return 0;
+}
\ No newline at end of file