aoc_omni/c/2024/1/historian_hysteria.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "../../lib/aoc.h"

int main() {
  char *line;
  int line_count = aoc_line_count();

  int left[line_count];
  int right[line_count];
  int index = 0;

  while ((line = aoc_read_line()) != NULL) {
    int l, r;
    sscanf(line, "%d %d", &l, &r);
    left[index] = l;
    right[index] = r;
    index++;
  }

  qsort(left, line_count, sizeof(int), aoc_sort_int);
  qsort(right, line_count, sizeof(int), aoc_sort_int);

  int sum = 0;

  for (int i = 0; i < line_count; i++) {
    sum += abs(left[i] - right[i]);
  }

  printf("Part 1: %d\n", sum);

  int similarity_score = 0;
  int j = 0;

  for (int i = 0; i < line_count; i++) {
    int right_count = 0;
    for (; j < line_count; j++) {
      if (left[i] == right[j]) right_count++;
      else if (left[i] < right[j]) break;
    }
    similarity_score += (left[i] * right_count);
  }

  printf("Part 2: %d\n", similarity_score);

  aoc_free();
  return 0;
}