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#include <stdio.h>
#include <stdlib.h>
#include <htable.h>
#include <crc32.h>
typedef struct {
int x;
int y;
} Point;
uint32_t point_hash(void *point) {
return crc32(0, point, sizeof(Point));
}
bool point_eq(void *x, void *y) {
Point *a = x, *b = y;
return (a->x == b->x) && (a->y == b->y);
}
typedef struct {
Point knots[10];
} State;
bool is_adjacent(Point p1, Point p2) {
if (abs(p1.x - p2.x) <= 1 && abs(p2.y - p1.y) <= 1) {
return true;
}
return false;
}
Point catchup(Point prev, Point new) {
int dx = new.x - prev.x;
int dy = new.y - prev.y;
int cx = 0, cy = 0;
if (dx > 0) cx = 1;
if (dx < 0) cx = -1;
if (dy > 0) cy = 1;
if (dy < 0) cy = -1;
return (Point){prev.x + cx, prev.y + cy};
}
void run_impl(State *s, HTable *record, int dx, int dy) {
s->knots[0].x += dx;
s->knots[0].y += dy;
for (int i = 1; i < 10; i++) {
if (is_adjacent(s->knots[i], s->knots[i-1])) {
continue;
}
s->knots[i] = catchup(s->knots[i], s->knots[i-1]);
if (i == 9) {
htable_insert(record , &(s->knots[i]));
}
}
}
void run(State *s, HTable *record, char direction, int step) {
int dx, dy;
switch (direction) {
case 'U':
dx = 0; dy = 1;
break;
case 'D':
dx = 0; dy = -1;
break;
case 'L':
dx = -1; dy = 0;
break;
case 'R':
dx = 1; dy = 0;
break;
default:
return;
}
for (int i = 0; i < step; i++) {
run_impl(s, record, dx, dy);
}
}
int count_htable(HTable *ht) {
int count = 0;
for (void *iter = htable_begin(ht);
iter != NULL;
iter = htable_next(ht, iter)) {
Point *p = iter;
count++;
}
return count;
}
int main() {
FILE *fp = fopen("input", "r");
State state = {0};
char direction;
int step;
HTable record;
htable_init(&record, sizeof(Point), -1, point_hash, point_eq);
htable_insert(&record, &state.knots[9]);
while (fscanf(fp, "%c %d", &direction, &step) != EOF) {
run(&state, &record, direction, step);
}
int count = count_htable(&record);
printf("%d\n", count);
return 0;
}
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