day 9 python part 1

day09/day09.py

@@ -0,0 +1,50 @@
+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 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))
+        
+

day09/sample

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+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2