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#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#if 0
#define PART_1
#else
#define PART_2
#endif
#if 0
#define FILE_PATH "example.txt"
#define T_WIDTH 5
#define T_HEIGHT 5
#else
#define FILE_PATH "input.txt"
#define T_WIDTH 100
#define T_HEIGHT 100
#endif
#define WIDTH 256
#define HEIGHT 256
#define OFFSET_X ((WIDTH/2) - (T_WIDTH/2))
#define OFFSET_Y ((HEIGHT/2) - (T_HEIGHT/2))
int board[WIDTH][HEIGHT];
int new_board[WIDTH][HEIGHT];
int enchance_alg[512];
void parse()
{
FILE *fp = fopen(FILE_PATH, "r");
if(!fp) {
fprintf(stderr, "ERROR: Could not open file: %s\n", FILE_PATH);
exit(EXIT_FAILURE);
}
char line[1024] = {0};
fgets(line, sizeof(line), fp);
for(int i = 0; i < 512; i++)
if(line[i] == '.')
enchance_alg[i] = 0;
else
enchance_alg[i] = 1;
fgets(line, sizeof(line), fp);
char ch;
int i = 0;
while((ch = getc(fp)) != EOF)
{
if(ch == '\n') continue;
else if(ch == '.')
board[i%T_WIDTH + OFFSET_X][i/T_WIDTH + OFFSET_Y] = 0;
else if(ch == '#')
board[i%T_WIDTH + OFFSET_X][i/T_WIDTH + OFFSET_Y] = 1;
i++;
}
fclose(fp);
}
int generate_index(int *vals)
{
int index = 0;
for(int i = 0; i < 9; i++)
{
index |= (vals[8-i] & 1)<< i;
}
return index;
}
void enchance()
{
for(int i = 0; i < HEIGHT; i++)
{
for(int j = 0; j < WIDTH; j++)
{
int vals[9];
for(int y = -1; y <= 1; y++)
for(int x = -1; x <= 1; x++)
{
int vals_i = (y+1) * 3 + (x+1);
if(i+y < 0 || i+y >= HEIGHT ||
j+x < 0 || j+x >= WIDTH)
vals[vals_i] = board[j][i];
else
vals[vals_i] = board[j+x][i+y];
}
new_board[j][i] = enchance_alg[generate_index(vals)];
}
}
memcpy(board, new_board, sizeof(board));
}
void print_board()
{
for(int i = 0; i < HEIGHT; i++)
{
for(int j = 0; j < WIDTH; j++)
if(board[j][i] == 0) putc('.', stdout);
else putc('#', stdout);
putc('\n', stdout);
}
}
void print_alg()
{
for(int i = 0; i < 512; i++)
{
if(enchance_alg[i] == 0) putc('.', stdout);
else putc('#', stdout);
}
putc('\n', stdout);
}
int main(void)
{
parse();
#ifdef PART_1
for(int i = 0; i < 2; i++)
#endif
#ifdef PART_2
for(int i = 0; i < 50; i++)
#endif
enchance();
int lit = 0;
for(int i = 0; i < HEIGHT; i++)
for(int j = 0; j < WIDTH; j++)
if(board[j][i] == 1) lit++;
printf("%d pixels are lit\n", lit);
return 0;
}
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