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


void print_numbers(int* numbers, int numbers_length);
bool are_safe(int* numbers, int numbers_length);
int find_first_unsafe(int* numbers, int numbers_length);

const int MAX_NUMBER_LENGTH = 16;
const int MAX_NUMBERS = 100;

int main(int argc, char** argv) {
	if (argc != 2) {
		fputs("Usage: ", stdout);
		fputs(argv[0], stdout);
		fputs(" <input file>\n", stdout);
		return 1;
	}

	FILE* file = fopen(argv[1], "r");

	unsigned int safe_count = 0;

	int line_no = 0;
	while (true) {
		char buffer[MAX_NUMBER_LENGTH];
		int buf_length = 0;
		int numbers[MAX_NUMBERS];
		int numbers_length = 0;
		int c;

		while (true) {
			c = fgetc(file);
			if (buf_length < MAX_NUMBER_LENGTH && c >= '0' && c <= '9') {
				buffer[buf_length++] = c;
				continue;
			}

			if (buf_length > 0 && numbers_length < MAX_NUMBERS) {
				buffer[buf_length] = 0;
				int number = atoi(buffer);
				numbers[numbers_length++] = number;
				buf_length = 0;
			}
			
			if (c == EOF || c == '\n') {
				break;
			}
		}

		if (numbers_length > 0 && are_safe(numbers, numbers_length)) {
			safe_count++;
		}

		line_no++;

		if (c == EOF) {
			break;
		}
	}

	printf("Safe count: %d\n", safe_count);

	fclose(file);
}

bool are_safe(int* numbers, int numbers_length) {
	print_numbers(numbers, numbers_length);

	int first_unsafe = find_first_unsafe(numbers, numbers_length);
	if (first_unsafe < 0) {
		return true;
	}

	int without[MAX_NUMBERS];
	memcpy(without, numbers, sizeof(int) * first_unsafe);
	memcpy(without + first_unsafe, numbers + first_unsafe + 1, sizeof(int) * (numbers_length - 1));

	if (find_first_unsafe(without, numbers_length - 1) < 0) {
		return true;
	}
	without[first_unsafe] = numbers[first_unsafe];

	return find_first_unsafe(without, numbers_length - 1) < 0;
}

int find_first_unsafe(int* numbers, int numbers_length) {
	if (numbers_length <= 1) {
		return -1;
	}

	int last_number = numbers[1];
	int last_delta = last_number - numbers[0];
	
	if (last_delta == 0 || abs(last_delta) > 3) {
		return 0;
	}

	for (int i = 2; i < numbers_length; i++) {
		int number = numbers[i];
		int delta = number - last_number;
		if (delta == 0 || abs(delta) > 3) {
			return i - 1;
		} else if (delta * last_delta < 0) {
			return i - 1;
		}
		last_number = number;
		last_delta = delta;
	}
	return -1;
}

void print_numbers(int* numbers, int numbers_length) {
	for (int i = 0; i < numbers_length; i++) {
		printf("%d ", numbers[i]);
	}
	puts("");
}