Advent-of-Code/2021/day4/solution-part1.c

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


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

typedef struct {
	unsigned int value;
	bool marked;
} Cell;

typedef struct {
	Cell cells[5][5];
} Grid;

unsigned int getEmptyLines(FILE *fp){
	char line[500];
	unsigned int emptyLines = 0;
	while (!feof (fp)){
		fgets(line, 500, fp);
		//Length of 1 because it's a new line character only
		if ( strlen(line) == 1 ) emptyLines ++;
	}
	return emptyLines;
}

//fp should be pointing to the start of the file as rounds are the first line
unsigned int countRounds(FILE *fp){
	unsigned int rounds=0;

		char ch = fgetc(fp);
		while ( ch != EOF ){
			switch (ch){
				case ',':
					rounds++;
					break;
				case '\n':
					rounds++;
					return rounds;
					break;
			}
			ch = fgetc(fp);
		}

	return rounds;
}

void printGrid(Grid *grid){
	for ( unsigned int row = 0; row < 5; row++ ){
		for ( unsigned int col = 0; col < 5; col++ ){
			if ( grid->cells[row][col].marked ) printf(ANSI_COLOR_RED);
			printf("%3i", grid->cells[row][col].value);
			if ( grid->cells[row][col].marked ) printf(ANSI_COLOR_RESET);
		}
		printf("\n");
	}
}

void printAllGrids(Grid grids[], unsigned int no){
	for( unsigned int i = 0; i<no; i++ ){
		printf("Grid %i\n", i);
		printGrid(&grids[i]);
		printf("\n");
	}
}

unsigned int sumUnmarked(Grid *grid){
	unsigned int sum = 0;
	for ( unsigned int row = 0; row < 5; row++ ){
		for ( unsigned int col = 0; col < 5; col++ ){
			if ( !grid->cells[row][col].marked ) sum += grid->cells[row][col].value;
		}
	}
	return sum;
}


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


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

		//The number of empty linse is the same as the number of grids
		unsigned int gridCount = getEmptyLines(fp);
		rewind(fp);

		Grid grids[gridCount];

		unsigned int rounds = countRounds(fp);
		int draws[rounds];
		memset( &draws, 0, rounds*sizeof(int) );
		rewind(fp);
		char ch;
		for ( unsigned int i = 0; i < rounds; i++ ){
			fscanf(fp, "%i%c,", &draws[i], &ch);
		}





		// Put all the numbers into the grid array
		unsigned int no;
		unsigned int grid = 0, row = 0, col = 0;
		while ( !feof(fp) && fscanf(fp, "%i", &no) ){
			grids[grid].cells[row][col].value = no;
			grids[grid].cells[row][col].marked = false;
			col = (col + 1) % 5;
			if ( col == 0 ) row = (row + 1) % 5;
			if ( col == 0 && row == 0 ) grid++;
		}

		//Start playing the game

		bool bingo=false;



		for (unsigned int round = 0; round < rounds && !bingo; round++){
			for( unsigned int grid = 0; grid < gridCount && !bingo; grid++ ){
				for( unsigned int row = 0; row < 5 && !bingo; row++ ){
					for( unsigned int col = 0; col < 5 && !bingo; col++ ){
						if ( grids[grid].cells[row][col].value == draws[round] ){
							grids[grid].cells[row][col].marked = true;
							//If we are above round 4, it's possible to have won
							if ( round > 4 ){
								bool maybebingorow=true;
								bool maybebingocol=true;
								// As soon as neither row or column is bingo, stop cheking
								for (unsigned int i = 0; ( maybebingocol || maybebingorow ) && i < 5; i++){
									// Go through the row and column for the matched number
									// As soon as we find one in the row or column that isn't marked, we know that won't be bingo
									if ( !grids[grid].cells[row][i].marked ) maybebingorow = false;
									if ( !grids[grid].cells[i][col].marked ) maybebingocol = false;
								}

								//If we get here and maybebingocol or maybebingorow is true, we have bingo
								if ( maybebingorow || maybebingocol ){
									bingo=true;
									unsigned int sum = sumUnmarked( &grids[grid] );
									printf("Bingo!!\n");
									printf("Round: %i\n", round);
									printf("Grid: %i\n", grid);
									printf("Unmarked Sum: %i\n", sum);
									printf("Last Called: %i\n", draws[round]);
									printf("Answer: %i\n", sum * draws[round]);
									printf("\n");
									printGrid(&grids[grid]);
								}

							}
						}
					}
				}
			}

			//No point checking before round 5
		}



		fclose(fp);



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