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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#if 0
#define PART_1
#else
#define PART_2
#endif
#if 0
#define FILE_PATH "example.txt"
#define RULES 2
int WIDTH = 11;
int HEIGHT = 15;
#else
#define FILE_PATH "input.txt"
#define RULES 12
int WIDTH = 1311;
int HEIGHT = 895;
#endif
#define BOARD_SZ ((WIDTH)*(HEIGHT))
int *board = NULL;
int rules_val[RULES] = {0};
int rules_axis[RULES] = {0}; // 0 is x; 1 is y
void parse()
{
FILE *fp = fopen(FILE_PATH, "r");
if(!fp) {
fprintf(stderr, "Could not open file: %s", FILE_PATH);
return;
}
board = malloc(BOARD_SZ*sizeof(int));
char line[256];
char *tok;
int read_rules = -1;
while(fgets(line, sizeof(line), fp) != NULL)
{
if(line[0] == '\n') {
read_rules = 0;
} else if(read_rules < 0) {
tok = strtok(line, ",");
int x = atoi(tok);
tok = strtok(NULL, ",");
int y = atoi(tok);
assert(strtok(NULL, ",") == NULL);
assert(x >= 0 && x < WIDTH);
assert(y >= 0 && y < HEIGHT);
board[y * WIDTH + x] = 1;
} else {
tok = strtok(line, "=");
rules_axis[read_rules] = (tok[11] == 'y');
tok = strtok(NULL, "=");
rules_val[read_rules] = atoi(tok);
read_rules++;
assert(strtok(NULL, "=") == NULL);
}
}
fclose(fp);
}
void fold(int rules_i)
{
int *board_cpy = malloc(BOARD_SZ*sizeof(int));
memcpy(board_cpy, board, BOARD_SZ*sizeof(int));
free(board);
int old_width = WIDTH;
if(rules_axis[rules_i] == 0) WIDTH = (WIDTH-1)/2;
else HEIGHT = (HEIGHT-1)/2;
board = malloc(BOARD_SZ*sizeof(int));
for(int i = 0; i < HEIGHT; i++)
{
for(int j = 0; j < WIDTH; j++)
{
int index = i * WIDTH + j;
int bc_index = i * old_width + j;
int mirror;
if(rules_axis[rules_i] == 0) {
mirror = i * old_width + (2*rules_val[rules_i] - j);
} else {
mirror = ((2*rules_val[rules_i] - i)
* old_width) + j;
}
board[index] =
board_cpy[bc_index] +
board_cpy[mirror];
}
}
free(board_cpy);
}
void print_board()
{
for(int i = 0; i < HEIGHT; i++)
{
for(int j = 0; j < WIDTH; j++)
{
if(board[i * WIDTH + j] == 0)
putc('.', stdout);
else
putc('#', stdout);
}
putc('\n', stdout);
}
}
void print_rules()
{
for(int i = 0; i < RULES; i++)
{
char axis;
if(rules_axis[i] == 0) axis = 'x';
else axis = 'y';
printf("fold along %c=%d\n", axis, rules_val[i]);
}
}
void part_1()
{
parse();
fold(0);
int visible = 0;
for(int i = 0; i < BOARD_SZ; i++)
{
if(board[i] > 0) visible++;
}
printf("%d dots are visible\n", visible);
}
void part_2()
{
parse();
for(int i = 0; i < RULES; i++)
fold(i);
print_board();
}
int main(void)
{
#ifdef PART_1
part_1();
#endif
#ifdef PART_2
part_2();
#endif
free(board);
return 0;
}
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