Advent-of-Code/2021/day9/solution-part2.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"

typedef struct Position {
	int value;
	bool marked;
	bool lowpoint;
} Position;

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;
}

bool isMinimum(int rows, int cols, Position grid[rows][cols], int row, int col){
	// Check above
	if ( row > 0 && grid[row-1][col].value <= grid[row][col].value ) return false;
	//check below
	if ( row < rows-1 && grid[row+1][col].value <= grid[row][col].value ) return false;
	// Check left
	if ( col > 0 && grid[row][col-1].value <= grid[row][col].value ) return false;
	//check below
	if ( col < cols-1 && grid[row][col+1].value <= grid[row][col].value ) return false;
	return true;
}

int cmp_asc_int(const void *a, const void *b) {
    return *(int*)a > *(int*)b;
}

unsigned int basinSize(int rows, int cols, Position grid[rows][cols], int row, int col){
	unsigned int ret = 0;
	if ( grid[row][col].value == 9 ){
		return 0;
	}

	ret++;
	grid[row][col].marked = true;

	//Check above
	if ( row > 0 && ! grid[row-1][col].marked )
		ret+=basinSize(rows, cols, grid, row-1, col);
	//Check below
	if ( row < rows-1 && ! grid[row+1][col].marked )
		ret+=basinSize(rows, cols, grid, row+1, col);
	// Check left
	if ( col > 0 && ! grid[row][col-1].marked )
		ret+=basinSize(rows, cols, grid, row, col-1);
	//check right
	if ( col < cols-1 && ! grid[row][col+1].marked )
		ret+=basinSize(rows, cols, grid, row, col+1);
	

	return ret;
}

void printGrid(int rows, int cols, Position grid[rows][cols]){
	for ( unsigned int row = 0; row < rows; row++ ){
		for ( unsigned int col = 0; col < cols; col++ ){
			if ( grid[row][col].lowpoint ) printf(ANSI_COLOR_RED);
			else if ( grid[row][col].marked ) printf(ANSI_COLOR_YELLOW);
			printf("%i", grid[row][col].value );
			if ( grid[row][col].marked ) printf(ANSI_COLOR_RESET);
		}
		printf("\n");
	}
}

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


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

		if ( fp == NULL ) {
			return 1;
		}

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

		Position grid[rows][cols];
		memset( &grid, 0, rows*cols*sizeof(Position) );

		unsigned int risk=0, row=0, col=0;

		unsigned int max[4] = {0};
		

		for ( char ch = fgetc(fp); EOF != ch; ch=fgetc(fp)){
			if ( ch == '\n' ){
				row++;
				col=0;
			} else {
				grid[row][col].value = atoi(&ch);
				col++;
			}
		}


		for ( unsigned int row = 0; row < rows; row++ ){
			for ( unsigned int col = 0; col < cols; col++ ){
				if ( isMinimum(rows, cols, grid, row, col) ){
					risk+= grid[row][col].value+1;
					grid[row][col].lowpoint = true;
					max[0] = basinSize(rows, cols, grid, row, col);
					qsort(max, 4, sizeof(unsigned int), cmp_asc_int);
				}
			}
		}


		unsigned int prouduct=1;
		printf("The largest 3 basins are:\n");
		for (unsigned int i = 1; i < 4; i++){
			printf("* %i\n", max[i]);
			prouduct *= max[i];

		}
		printf("\nProduct is %i\n", prouduct);
		



		fclose(fp);




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