adventofcode2022/day09/day09.py

H = (0,0)
T = (0,0)
def go(p, dir):
    x,y = p
    if dir == "U":
        y += 1
    if dir == "D":
        y -= 1
    if dir == "L":
        x -= 1
    if dir == "R":
        x += 1
    return x,y

def follow():
    if H == T:
        return T
    if abs(H[0] - T[0]) <= 1 and abs(H[1] - T[1]) <= 1:
        return T
    if H[1] == T[1]:
        x,y = T
        x = H[0] - sgn(H[0] - T[0])
        return x,y
    if H[0] == T[0]:
        x,y = T
        y = H[1] -  sgn(H[1]-T[1])
        return x,y
    # diagonal
    x,y = T
    x += sgn(H[0] - T[0])
    y += sgn(H[1] - T[1])
    return x,y

def follow2(h, t):
    if h == t:
        return t
    if abs(h[0] - t[0]) <= 1 and abs(h[1] - t[1]) <= 1:
        return t
    if h[1] == t[1]:
        x,y = t
        x = h[0] - sgn(h[0] - t[0])
        return x,y
    if h[0] == t[0]:
        x,y = t
        y = h[1] -  sgn(h[1]-t[1])
        return x,y
    # diagonal
    x,y = t
    x += sgn(h[0] - t[0])
    y += sgn(h[1] - t[1])
    return x,y

def sgn(x):
    if x==0: return 0
    if x > 0: return 1
    return -1

visited = set([T])
for line in open("input"):
    dir, count = line.split()
    count = int(count)
    for _ in range(count):
        H = go(H, dir)
        T = follow()
        visited.add(T)
        #print(H,T)
print(len(visited))
        

R = [(0,0)]*10
visited = set([R[-1]])
for line in open("input"):
    dir, count = line.split()
    count = int(count)
    for _ in range(count):
        R[0] = go(R[0], dir)
        for i in range(1,len(R)):
            t = follow2(R[i-1], R[i])
            if t == R[i]:
                break
            R[i] = t
        visited.add(R[-1])
        print(R)
print(len(visited))