day 8 python slight cleanup

day08/sol2.py

@@ -6,36 +6,30 @@ scores = []
 for ii in range(len(data)):
     for jj in range(len(data[ii])):
         top = data[ii][jj]
-        h = -1
         a = 0
+        i = ii
         for j in range(jj+1, len(data[ii])):
             a += 1
-            h = data[ii][j]
-            if h >= top:
+            if data[i][j] >= top:
                 break
 
         b = 0
-        h = -1
         for j in reversed(range(0, jj)):
             b += 1
-            h = data[ii][j]
-            if h >= top:
+            if data[i][j] >= top:
                 break
 
+        j = jj
         c = 0
-        h = -1
         for i in range(ii+1, len(data)):
             c += 1
-            h = data[i][jj]
-            if h >= top:
+            if data[i][j] >= top:
                 break
 
         d = 0
-        h = -1
         for i in reversed(range(0, ii)):
             d += 1
-            h = data[i][jj]
-            if h >= top:
+            if data[i][j] >= top:
                 break
 
         print(ii,jj,a,b,c,d)

day09/day09.py

@@ -0,0 +1,42 @@
+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)

day09/sample

@@ -0,0 +1,8 @@
+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2