02.c


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#include <stdio.h>
#include <err.h>
#include <string.h>
#include "input.h"

#define INPUT "input/02.txt"

enum direction { forward, up, down };

struct submarine_move {
	enum direction dir;
	int length;
};

void parse_move(char* string, struct submarine_move* move) {
	if(*string == 'f')
		move->dir = forward;
	else if(*string == 'u')
		move->dir = up;
	else if(*string == 'd')
		move->dir = down;
	else
		err(1, "direction inconnue %c", *string);

	size_t stringLength = strlen(string);
	char digit = string[stringLength - 2];
	if(digit < '0' || digit > '9')
		err(1, "longueur inconnue %c", digit);
	move->length = digit - '0';
}

void part1(struct input_str* input) {
	struct submarine_move currentMove;
	long forwardDst = 0;
	long downDst = 0;
	for(size_t i = 0; i < input->line_count; i++) {
		parse_move(input->lines[i], &currentMove);
		switch(currentMove.dir) {
			case forward:
				forwardDst += currentMove.length;
				continue;
			case up:
				downDst -= currentMove.length;
				continue;
			case down:
				downDst += currentMove.length;
				continue;
		}
	}
	printf("%ld\n", forwardDst * downDst);
}

void part2(struct input_str* input) {
	struct submarine_move currentMove;
	long forwardDst = 0;
	long downDst = 0;
	long aim = 0;
	for(size_t i = 0; i < input->line_count; i++) {
		parse_move(input->lines[i], &currentMove);
		switch(currentMove.dir) {
			case forward:
				forwardDst += currentMove.length;
				downDst += currentMove.length * aim;
				continue;
			case up:
				aim -= currentMove.length;
				continue;
			case down:
				aim += currentMove.length;
				continue;
		}
	}
	printf("%ld\n", forwardDst * downDst);
}

int main() {
	// read input data
	struct input_str input;
	input_str_read(&input, INPUT);

	// do stuff
	part1(&input);
	part2(&input);

	// cleanup & exit
	input_str_free(&input);
	return 0;
}