2022/day09.awk


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BEGIN {
	t[0,0] = 1;
}
function abs(x) {
	if (x < 0) return -x;
	return x;
}
function step() {
	rx = tx-hx;
	ry = ty-hy;
	if (abs(rx) <= 1 && abs(ry) <= 1) return;
	if (rx == 0) {
		ty += (ry < 0 ? +1 : -1);
	} else if (ry == 0) {
		tx += (rx < 0 ? +1 : -1);
	} else {
		tx += (rx < 0 ? +1 : -1);
		ty += (ry < 0 ? +1 : -1);
	}
	t[tx,ty] = 1;
}
{
	dx = 0;
	dy = 0;
	if ($1 == "U") dy = -1;
	if ($1 == "D") dy = +1;
	if ($1 == "L") dx = -1;
	if ($1 == "R") dx = +1;
	for (i = 1; i <= $2; ++i) {
		hx += dx;
		hy += dy;
		step();
	}
}
END {
	for (i in t) {
		sum++;
	}
	print sum;
}