43 lines
978 B
Python
43 lines
978 B
Python
def go(p, dir):
|
|
x,y = p
|
|
if dir == "U": y += 1
|
|
elif dir == "D": y -= 1
|
|
elif dir == "L": x -= 1
|
|
elif dir == "R": x += 1
|
|
return x,y
|
|
|
|
def follow(h, t):
|
|
if abs(h[0] - t[0]) > 1 or abs(h[1] - t[1]) > 1:
|
|
x,y = t
|
|
x += sgn(h[0] - t[0])
|
|
y += sgn(h[1] - t[1])
|
|
t = x,y
|
|
return t
|
|
|
|
def sgn(x):
|
|
return (x > 0) - (x < 0)
|
|
|
|
def solve(n):
|
|
R = [(0,0)]*n
|
|
visited = set([R[-1]])
|
|
for line in open("input"):
|
|
dir, count = line.split()
|
|
for _ in range(int(count)):
|
|
R[0] = go(R[0], dir)
|
|
for i in range(1, len(R)):
|
|
t = follow(R[i-1], R[i])
|
|
if t == R[i]:
|
|
# optimization: if a knot doesn't move,
|
|
# none of the knots after it will either
|
|
break
|
|
R[i] = t
|
|
visited.add(R[-1])
|
|
#print(R)
|
|
return len(visited)
|
|
|
|
A1 = solve(2)
|
|
print(A1)
|
|
|
|
A2 = solve(10)
|
|
print(A2)
|