2025 c day 5

c/2025/5/problem.c

@@ -0,0 +1,94 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include "../../lib/aoc.h"
+
+typedef struct Range {
+  uint64_t begin;
+  uint64_t end;
+} Range;
+
+int sort_range(const void *a, const void *b) {
+  return (*(Range*) a).begin > (*(Range*) b).begin ? 1 :
+    (*(Range*) a).begin < (*(Range*) b).begin ? -1 : 0;
+}
+
+bool id_in_range(uint64_t id, Range *ranges, int range_count) {
+  for (int i = 0; i < range_count; i++) {
+    if (id >= ranges[i].begin && id <= ranges[i].end) return true;
+  }
+
+  return false;
+}
+
+bool combine_ranges(Range *r1, Range *r2) {
+  if (r2->begin > r1->end || r1->begin > r2->end) return false;
+  
+  r1->begin = r1->begin > r2->begin ? r2->begin : r1->begin;
+  r1->end = r1->end < r2->end ? r2->end : r1->end;
+  r2->begin = 0;
+  r2->end = 0;
+  return true;
+}
+
+int main() {
+  char *line;
+
+  Range ranges[200];
+  uint64_t ids[1000];
+
+  int index = 0;
+  int range_count;
+  int id_count;
+  bool reading_ids = false;
+  while ((line = aoc_read_line()) != NULL) {
+    if (reading_ids) {
+      sscanf(line, "%lu", &(ids[index]));
+      index++;
+    } else {
+      if (strlen(line) == 0) {
+	reading_ids = true;
+	range_count = index;
+	index = 0;
+      } else {
+	sscanf(line, "%lu-%lu", &(ranges[index].begin), &(ranges[index].end));
+	index++;
+      }
+    }
+  }
+
+  id_count = index;
+  int valid_id_count = 0;
+
+  for (int i = 0; i < id_count; i++) {
+    if (id_in_range(ids[i], ranges, range_count)) valid_id_count++;
+  }
+
+  printf("Part 1: %d\n", valid_id_count);
+
+  qsort(ranges, range_count, sizeof(Range), sort_range);
+  
+  for (int i = 0; i < range_count - 1;) {
+    bool combined = combine_ranges(&ranges[i], &ranges[i + 1]);
+    if (combined) {
+      memcpy(&(ranges[i+1]), &(ranges[i+2]), sizeof(Range) * (range_count - (i + 1)));
+      range_count--;
+    } else {
+      i++;
+    }
+  }
+
+  uint64_t covered_id_count = 0;
+
+  for (int i = 0; i < range_count; i++) {
+    covered_id_count += (ranges[i].end - ranges[i].begin + 1);
+  }
+
+  printf("Part 2: %lu\n", covered_id_count);
+
+  aoc_free();
+
+  return 0;
+}