Advent-of-Code/2021/day9/solution-part1.c

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


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

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);

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

		unsigned int risk=0;
		unsigned int row=0, col=0;
		for ( char ch = fgetc(fp); EOF != ch; ch=fgetc(fp)){
			if ( ch == '\n' ){
				row++;
				col=0;
			} else {
				grid[row][col] = 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]+1;
				}
			}
		}

		printf("Total risk at lowpoints: %i\n", risk);




		fclose(fp);




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