adventofcode2025/adventofcodeday6.c at main · pPyrius/adventofcode2025 · GitHub

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

void do_moltiplication(char **lines, int i, int n, ulong *sum) {
  ulong product = 1;
  ulong j;
  int offset;
  for (int i = 0; i < n; i++) {
    sscanf(lines[i], "%lu %n", &j, &offset);
    product *= j;
    lines[i] += offset;
  }
  *sum += product;
}

void do_sum(char **lines, int i, int n, ulong *sum) {
  ulong j;
  int offset;
  for (int i = 0; i < n; i++) {
    sscanf(lines[i], "%lu %n", &j, &offset);
    *sum += j;
    lines[i] += offset;
  }
}

void perform_calculations(char **lines, int n) {
  ulong sum = 0;
  char operand = 0;
  int loop = 1;
  int i = 0;
  while (loop) {
    sscanf(lines[n - 1] + i, "%c", &operand);
    switch (operand) {
    case 43:
      do_sum(lines, i, n - 1, &sum);
      break;
    case 42:
      do_moltiplication(lines, i, n - 1, &sum);
      break;
    }
    i++;
    if (lines[n - 1][i] == '\0') {
      loop = 0;
    }
  }
  printf("Sum: %lu\n", sum);
}

int main(void) {
  char **lines = NULL;
  size_t len = 0;
  FILE *file = fopen("input", "r");
  if (file == NULL) {
    printf("Error opening file\n");
    return 1;
  }
  int i;
  int nread;
  for (i = 0, nread = 0; nread != -1; i++) {
    lines = realloc(lines, (i + 1) * sizeof(char *));
    nread = (int)getline(&lines[i], &len, file);
  }
  perform_calculations(lines, i - 1);
  fclose(file);
}