day 15 part 2 alternate solution

day15/clip.py

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+import pyclipper # https://pypi.org/project/pyclipper/
+
+data = []
+for line in open("input"):
+    words = line.replace(":", "").replace(",","").split()
+    coords = [int(w[w.index('=')+1:]) for w in words if '=' in w]
+    data.append(coords)
+
+
+pc = pyclipper.Pyclipper()
+for sx,sy,bx,by in data:
+    dx = abs(sx-bx)
+    dy = abs(sy-by)
+    d = dx+dy
+    pc.AddPath([(sx+d,sy),(sx,sy+d),(sx-d,sy),(sx,sy-d)], pyclipper.PT_CLIP, closed=True)
+
+M = 4000000
+pc.AddPath([(0,0),(M,0),(M,M),(0,M)], pyclipper.PT_SUBJECT, closed=True)
+
+solution = pc.Execute(pyclipper.CT_DIFFERENCE, pyclipper.PFT_NONZERO, pyclipper.PFT_NONZERO)
+
+# should return a single small polygon shaped like a diamond
+# the answer we want is the point at the center of the diamond
+
+assert len(solution) == 1
+assert pyclipper.Area(solution[0]) < 4
+
+def avg(ns):
+    return sum(ns)/len(ns)
+
+for p in solution:
+    x = avg([x for x,y in p])
+    y = avg([y for x,y in p])
+    print(x,y)
+    print("frequency =",M*x + y)