Advent of code d1

2025-12-01

I never manage to finish advent of code. Here is my C solution to day 1.

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

#define MAX_LINE_LENGTH 99

int main() {
	int result = 50;
	int password = 0;
	FILE *f;

	char line[MAX_LINE_LENGTH];
	const char *filename = "day1-input.txt";
	f = fopen(filename, "r");
	if(f == NULL) {
		perror("error opening");
		return 1;
	}
	while(fgets(line, MAX_LINE_LENGTH, f) != NULL) {
		size_t len = strlen(line);
		if(len > 1 && (line[0] == 'L' || line[0] == 'R')) {
			int n = atoi(line + 1);
			for(int i = 0; i < n; i++) {
				if(line[0] == 'L') {
					result--;
					if(result < 0) result = 99;
				} else {
					result++;
					if(result > 99) result = 0;
				}
				// increment here for second phase
				// if(result == 0) password++;
			}
			// increment here for first phase
			if(result == 0) password++;
		}
	}
	fclose(f);

	printf("%d\n", password);
	return 0;
}