advent2021

Advent of Code 2021 Solutions
git clone git://bsandro.tech/advent2021
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commit c2f92267749224cda5d4854ba1a4820306753202
parent 548678ce56cc166d3495816095aed4049fbf7103
Author: bsandro <brian.drosan@gmail.com>
Date:   Sat, 11 Dec 2021 11:42:23 +0200

Day 11, puzzle 1

Diffstat:
Aday11/Makefile | 25+++++++++++++++++++++++++
Aday11/input.txt | 10++++++++++
Aday11/main.c | 30++++++++++++++++++++++++++++++
Aday11/puzzle.c | 114+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Aday11/test.txt | 10++++++++++
5 files changed, 189 insertions(+), 0 deletions(-)

diff --git a/day11/Makefile b/day11/Makefile @@ -0,0 +1,25 @@ +NAME=$(shell basename ${PWD}) +SRC=$(wildcard *.c ../common/*.c) +DEPS:=$(wildcard *.h ../common/*.h) +OBJ:=$(SRC:.c=.o) +CFLAGS=-O2 -std=c99 -Werror -Wall -Wextra -I. -I../common +LDFLAGS=-lc + +all: $(NAME) + +.PHONY: clean run + +clean: + rm -f $(OBJ) $(NAME) + +%.o : %.c $(DEPS) + @$(CC) $(CFLAGS) -c $< -o $@ + +$(NAME): $(OBJ) + @$(CC) $(OBJ) -o $@ $(LDFLAGS) + +run: $(NAME) + @./$(NAME) input.txt + +test: $(NAME) + @./$(NAME) test.txt diff --git a/day11/input.txt b/day11/input.txt @@ -0,0 +1,10 @@ +4438624262 +6263251864 +2618812434 +2134264565 +1815131247 +2612457325 +8585767584 +7217134556 +2825456563 +8248473584 diff --git a/day11/main.c b/day11/main.c @@ -0,0 +1,30 @@ +#include <stdio.h> +#include <time.h> +#include <string.h> + +void puzzle(const char *filename, long long *res1, long long *res2); +void puzzle_test(const char *filename, long long *res1, long long *res2); + +int main(int argc, char *argv[]) { + printf("Advent of Code: day 11\n"); + double time_start = clock(); + + if (argc <= 1) { + printf("Usage: %s inputfile.txt\n", argv[0]); + return -1; + } + + const char *filename = argv[1]; + long long counter1 = -1; + long long counter2 = -1; + + puzzle(filename, &counter1, &counter2); + + printf("Puzzle #1: %lld\n", counter1); + printf("Puzzle #2: %lld\n", counter2); + + double elapsed = clock() - time_start; + printf("Elapsed: %f\n", elapsed / CLOCKS_PER_SEC); + + return 0; +} diff --git a/day11/puzzle.c b/day11/puzzle.c @@ -0,0 +1,114 @@ +#define _DEFAULT_SOURCE + +#include <stdio.h> +#include <stdlib.h> +#include <errno.h> +#include <string.h> +#include <strings.h> +#include <assert.h> +#include <ctype.h> + +#include "util.h" + +#define STR_LEN 1024 +#define GRID_WIDTH 10 +#define GRID_HEIGHT 10 +#define STEPS 100 + +typedef int octopuses_t[GRID_HEIGHT][GRID_WIDTH]; + +void step(octopuses_t *octopuses); +void print(octopuses_t *octopuses); +void light(octopuses_t *octopuses, int x, int y); +void process(octopuses_t *octopuses, int x, int y); +int normalize(octopuses_t *octopuses); + +void puzzle(const char *filename, long long *result1, long long *result2) { + FILE *infile = fopen(filename, "r"); + if (infile == NULL) { + fprintf(stderr, "fopen() error: %s\n", strerror(errno)); + return; + } + + char buf[STR_LEN] = {0}; + unsigned int line_num = 0; + octopuses_t octopuses = {0}; + + *result1 = 0; + *result2 = 0; + + while (fgets(buf, STR_LEN, infile) != NULL) { + size_t len = strlen(buf); + assert(len >= GRID_WIDTH); + for (int i = 0; i < GRID_WIDTH; ++i) { + assert(isdigit(buf[i])); + octopuses[line_num][i] = buf[i] - '0'; + } + ++line_num; + bzero(buf, STR_LEN); + } + + int flashes = 0; + + for (int s = 1; s <= STEPS; ++s) { + step(&octopuses); + flashes += normalize(&octopuses); + } + + *result1 = flashes; + + // mutiny! ignoring feof/ferror. + fclose(infile); +} + +void step(octopuses_t *octopuses) { + for (int y = 0; y < GRID_HEIGHT; ++y) { + for (int x = 0; x < GRID_WIDTH; ++x) { + process(octopuses, x, y); + } + } +} + +void process(octopuses_t *octopuses, int x, int y) { + int o = ++(*octopuses)[y][x]; + if (o == 10) { + light(octopuses, x, y); + } +} + +void light(octopuses_t *octopuses, int x, int y) { + if (y > 0) process(octopuses, x, y-1); + if (y < GRID_HEIGHT-1) process(octopuses, x, y+1); + if (x > 0) { + process(octopuses, x-1, y); + if (y > 0) process(octopuses, x-1, y-1); + if (y < GRID_HEIGHT-1) process(octopuses, x-1, y+1); + } + if (x < GRID_WIDTH-1) { + process(octopuses, x+1, y); + if (y > 0) process(octopuses, x+1, y-1); + if (y < GRID_HEIGHT-1) process(octopuses, x+1, y+1); + } +} + +int normalize(octopuses_t *octopuses) { + int flashes = 0; + for (int y = 0; y < GRID_HEIGHT; ++y) { + for (int x = 0; x < GRID_WIDTH; ++x) { + if ((*octopuses)[y][x] > 9) { + (*octopuses)[y][x] = 0; + ++flashes; + } + } + } + return flashes; +} + +void print(octopuses_t *octopuses) { + for (int y = 0; y < GRID_HEIGHT; ++y) { + for (int x = 0; x < GRID_WIDTH; ++x) { + printf("%2d", (*octopuses)[y][x]); + } + printf("\n"); + } +} diff --git a/day11/test.txt b/day11/test.txt @@ -0,0 +1,10 @@ +5483143223 +2745854711 +5264556173 +6141336146 +6357385478 +4167524645 +2176841721 +6882881134 +4846848554 +5283751526