AoC2023/day3/day3a.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <math.h>
#include <ctype.h>

int rows = 0;
int columns;

typedef struct {
	int pos[2];
	int sum;
	int len;
	
} number;
typedef struct {
	int length;
	int listSize;
	long unsigned int gearSum;
	number numbers[];
} numberList;

numberList *findNumbers();
numberList *addNumber(numberList *list, int sum, int len, int col, int row);
int readNumber(char **schematic, int *len, int *col, int row);
unsigned long int checkNumbers(char **schematic, numberList *list, int rows, int columns);

int main ()
{
	int columnsc = 0;
	char c;
	
	numberList *list = malloc(sizeof(int) * 2 + sizeof(long unsigned int) + sizeof(number) * 8);
	list->listSize = 8;
	list->length = 0;

	FILE *input;
	input = fopen("./input", "r");

	// see dimensions of file
	while ((c = fgetc(input)) != EOF) {
		if (c == '\n') {
			rows++;
			if (columns < columnsc)
				columns = columnsc;
			columnsc = 0;
		} else { // I could probably not do this every row but w/e
			columnsc++;
		}
	}

	// allocate memory for the char array array
	char **schematic = malloc(columns * sizeof(char*));
	for (int i = 0; i < columns; i++)
		schematic[i] = malloc(rows * sizeof(char*));

	// read the file again to fill up the array
	rewind(input);
	for (int row = 0; row < rows; row++) {
		for (int col = 0; col < columns; col++) {
			schematic[col][row] = fgetc(input);
		}
		fgetc(input); // discard \n	
	}
	fclose(input);

	// just print the damn thing
	// for (int row = 0; row < rows; row++) {
	// 	for (int col = 0; col < columns; col++) {
	// 		printf("%c", schematic[col][row]);
	// 	}
	// 	printf("\n");
	// }
	printf("\nRows: %d\nColumns: %d\n\n", rows, columns);

	list = findNumbers(schematic, list);
	printf("Found %d numbers.\n", list->length);
	
	printf("Total sum is %lu.\n", checkNumbers(schematic, list, rows, columns));
	printf("Gear ratio sum is %lu.\n", list->gearSum);
}

// Test gear: count how many numbers are around it, if 2, multiply and return product
int checkGear(char **schematic, int col, int row)
{
	int numbers[2];
	int foundNumbers = 0;
	int ratio = 0;
	for (int y = row - 1; y <= row + 1; y++) {
		if (y < 0) y++;
		for (int x = col + 1; x >= col - 1; x--) {
			if (x >= columns) x--;
			if (x < 0) break; 

			while (x < columns - 1 &&(schematic[x][y] >= '0' && schematic[x][y] <= '9'
			                       && schematic[x + 1][y] >= '0' && schematic[x + 1][y] <= '9')) {
				x++;
			}
			if (schematic[x][y] >= '0' && schematic[x][y] <= '9') {
				if (foundNumbers >= 2) {
					foundNumbers++;
				}

				int len = 0; // TODO: Really not needed
				numbers[foundNumbers] = readNumber(schematic, &len, &x, y);
				foundNumbers++;
			}

		}
	}
	
	if (foundNumbers == 2) {
		ratio = numbers[0] * numbers[1];
		printf("Values: %d and %d = %d\n", numbers[0], numbers[1], numbers[0] * numbers[1]);
	}
	return ratio;
}

// Why is len a ptr? because I need to return two values duh
int readNumber(char **schematic, int *len, int *col, int row) 
{
	int sum = 0;
	while (*col >= 0 && schematic[*col][row] >= '0' && schematic[*col][row] <= '9') {
		sum += (schematic[*col][row] - '0') * (int)pow(10, *len);
		(*len)++;
		(*col)--;
	}

	(*col)++;
	return sum;
}
// for each number in list, check adjacent fields
unsigned long int checkNumbers(char **schematic, numberList *list, int rows, int columns)
{
	unsigned long int sum = 0;
	int previous;
	for(int i = 0; i < list->length; i++) {
		// make sure col or row is never too high / low
		number num = list->numbers[i];
		for (int row = num.pos[1] - 1; row <= num.pos[1] + 1; row++) {
			if (row < 0) row++;
			if (row >= rows) break;
			for (int col = num.pos[0] - 1; col < num.pos[0] + num.len + 1; col++) {
				if (col  < 0) col++;
				if (col >= columns) break;
				char c = schematic[col][row];

				if (!isdigit(c) && c != '.'){
					previous = num.sum;
					sum += num.sum;
					goto nextIteration;
				}
			}
		}
		nextIteration:
	}

	return sum;
	
}

// för varje position i 2D-arrayen, om siffra, leta efter dess "start" genom att gå åt vänster
// lagra en "pekare" till starten, längden (antalet siffror) och totalvärdet
// ^ gör en lista av dessa
// hoppa till slutet av den man hittade och iterera vidare genom sökfältet
numberList *findNumbers(char **schematic, numberList *list)
{
	for (int row = 0; row < rows; row++) {
		for (int col = columns - 1; col >= 0; col--) {
			if (schematic[col][row] == '*') {
				int sum = checkGear(schematic, col, row);
				printf("%d + %d = ", list->gearSum, sum);
				list->gearSum += sum;
				printf("%d\n", list->gearSum);
			}
			if (schematic[col][row] >= '0' && schematic[col][row] <= '9') {
				int len = 0;
				int sum = readNumber(schematic, &len, &col, row);
				list = addNumber(list, sum, len, col, row);
			}
		}
	}

	return list;
}

numberList *addNumber(numberList *list, int sum, int len, int col, int row)
{
	if (list->length >= list->listSize) {
		list->listSize = list->listSize * 2;
		printf("Resizing!\n", list->listSize, list->length);
		printf("size: %d length: %d\n", list->listSize, list->length);
		list = realloc(list, list->listSize * sizeof(number) + sizeof(int) * 2 + sizeof(long unsigned int));
	}
	list->numbers[list->length].pos[0] = col + 1;
	list->numbers[list->length].pos[1] = row;
	list->numbers[list->length].sum = sum;
	list->numbers[list->length].len = len;
	list->length++;

	return list;
}