Advent-of-Code/2021/day15/solution-part1.c

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

#define ANSI_COLOR_RED     "\x1b[31m"
#define ANSI_COLOR_YELLOW  "\x1b[33m"
#define ANSI_COLOR_RESET   "\x1b[0m"

#define MAX(a, b) ((a) < (b) ? (b) : (a))
#define MIN(a, b) ((a) < (b) ? (a) : (b))

typedef struct Square Square;

struct Square{
	unsigned int risk;
	Square *previous;
	unsigned int distanceFromStart;
	Square *up;
	Square *down;
	Square *left;
	Square *right;
	bool onShortestPath;
	bool used;
};


int countRows(FILE *fp){
	unsigned int lines=0;

	while (EOF != (fscanf(fp, "%*[^\n]"), fscanf(fp,"%*c")))
		++lines;
	return lines;
}

int countCols(FILE *fp){
	unsigned int lineLength=0;
	char ch = fgetc(fp);
	while ( ch != '\n' ){
		lineLength++;
		ch = fgetc(fp);
	}
	return lineLength;
}

void printGrid( unsigned int cols, unsigned int rows, Square **grid){
	for ( unsigned int row = 0; row < rows; row++ ){
		for ( unsigned int col = 0; col < cols; col++ ){
			if ( grid[col][row].onShortestPath ) printf(ANSI_COLOR_RED);
			printf("%i ", grid[col][row].risk);
			if ( grid[col][row].onShortestPath ) printf(ANSI_COLOR_RESET);
		}
		printf("\n");
	}
}

void maybeUpdate(Square *current, Square *adjacent){
	if ( adjacent == NULL ) return ;
	if ( current->distanceFromStart + adjacent->risk < adjacent->distanceFromStart ){
		adjacent->distanceFromStart = current->distanceFromStart + adjacent->risk;
		adjacent->previous = current;
	}
}
void markAdjacent(Square *current){
	unsigned int currentDistance = current->distanceFromStart;
	maybeUpdate(current, current->up);
	maybeUpdate(current, current->down);
	maybeUpdate(current, current->left);
	maybeUpdate(current, current->right);
}

Square* getLowestEndScoredSquare( Square**grid, unsigned int cols, unsigned int rows ){
	Square *lowest = &grid[cols][rows];
	for ( unsigned int row = 0; row < rows; row++ ){
		for ( unsigned int col = 0; col < cols; col++ ){
			//printf("%i\n",lowest->distanceFromStart);
			if ( (!grid[col][row].used) && (grid[col][row].distanceFromStart < lowest->distanceFromStart) ){
				printf("col: %i row: %i\n",col,row);
				lowest = &grid[col][row];
			}
		}
	}
	return lowest;
}


int main( int argc, char *argv[] ){
	if( argc == 2 ) {


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

		unsigned int cols=countCols(fp);
		rewind(fp);
		unsigned int rows=countRows(fp);
		rewind(fp);

		Square **grid=(Square**)malloc( cols * sizeof(Square *));
		for(unsigned int i=0; i<=rows;i++) {
			grid[i]=(Square*)malloc( (rows) *sizeof(Square));
			memset(grid[i], 0, sizeof(Square) * ( rows ));
		}

		char ch;
		unsigned int row=0, col=0;
		while ( !feof(fp) && fscanf(fp, "%c", &ch) ){
			if ( ch == '\n' ){
				col = 0;
				row++;
				continue;
			}
			grid[col][row].risk = atoi(&ch);
			grid[col][row].distanceFromStart = ~0;
			grid[col][row].up = ( row > 0 ) ? &grid[col][row-1] : NULL;
			grid[col][row].down = ( row < rows - 1 ) ? &grid[col][row+1] : NULL;
			grid[col][row].left = ( col > 0 ) ? &grid[col-1][row] : NULL;
			grid[col][row].right = ( col < cols - 1 ) ? &grid[col+1][row] : NULL;
			grid[col][row].onShortestPath = false;
			grid[col][row].used = false;
			col++;
		}


		Square *current = &grid[0][0];
		unsigned int i = 0;
		while (true){
			markAdjacent(current);
			current->used = true;
			if (current == &grid[cols-1][rows-1] ) break;
			current = getLowestEndScoredSquare(grid, cols, rows);
			i++;
			printf("---\n");
		}

		unsigned int total = 0;

		while ( true ){
			current->onShortestPath = true;
			total += current->risk;
			if ( current != &grid[0][0] )
				current = current->previous;
			else
				break;
		}


		printGrid(cols, rows, grid);
		//grid[0][0].distanceFromStart = 0;
		printf("Total risk: %i\n", total - grid[0][0].risk);
		//markAdjacent(grid, 0, 0);


		fclose(fp);
		return 0;
	} else {
		printf("You need to provide a file\n");
		return 1;
	}
}