day 10 python rewrite

pass around an iterator of X states instead of using a callback and
global variables.

day10/sol.py

@@ -1,35 +1,39 @@
+import itertools
+import time
 
-cycle = 0
-X = 1
-T = 0
-def step():
-    global T
-    global cycle
-    cycle += 1
-    if cycle in (20, 60, 100, 140, 180, 220):
-        ss = cycle * X
-        T += ss
-
-    px = (cycle-1) % 40
-    if abs(X - px) <= 1:
-        # sprite is visible
-        img.append('#')
-    else:
-        img.append(' ')
-
-
-img = []
-
-for line in open("input"):
+def run(input):
+    x = 1
+    for line in input:
         ins = line.strip()
         if ins == "noop":
-        step()
-    else:
-        step()
-        step()
-        X += int(line.split()[1])
+            yield x
+        else: # addx <num>
+            yield x
+            yield x
+            x += int(line.split()[1])
 
-print (T)
+def signal(xs):
+    t = 0
+    for cycle, x in enumerate(xs, start=1):
+        if cycle % 40 == 20:
+            signal_strength = cycle * x
+            t += signal_strength
+    return t
 
-for i in range(0, len(img), 40):
-    print(''.join(img[i:i+40]))
+def render(xs):
+    xs = iter(xs)
+    while True:
+        img = []
+        for pos, x in enumerate(itertools.islice(xs, 40)):
+            visible = x-1 <= pos <= x+1
+            img.append(' #'[visible])
+        if not img: return
+        yield ''.join(img)
+
+xs = list(run(open("input")))
+print(signal(xs))
+
+img = render(xs)
+for line in img:
+    print(line)
+    time.sleep(.1) # :)