day 15 part 2 alternate solution

day15/clip.py

@@ -0,0 +1,35 @@
+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)

day15/input

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+Sensor at x=325337, y=2568863: closest beacon is at x=-518661, y=2000000
+Sensor at x=3988825, y=837820: closest beacon is at x=4305648, y=2127118
+Sensor at x=1611311, y=2053174: closest beacon is at x=2827226, y=1579510
+Sensor at x=101890, y=3940049: closest beacon is at x=955472, y=3457514
+Sensor at x=3962702, y=2558425: closest beacon is at x=4226981, y=2604726
+Sensor at x=2957890, y=2160813: closest beacon is at x=2827226, y=1579510
+Sensor at x=3907456, y=3325610: closest beacon is at x=3696221, y=3226373
+Sensor at x=3354177, y=3435919: closest beacon is at x=3696221, y=3226373
+Sensor at x=3997379, y=3071868: closest beacon is at x=3696221, y=3226373
+Sensor at x=145143, y=1714962: closest beacon is at x=-518661, y=2000000
+Sensor at x=611563, y=3148864: closest beacon is at x=955472, y=3457514
+Sensor at x=3080405, y=3904777: closest beacon is at x=3696221, y=3226373
+Sensor at x=644383, y=10732: closest beacon is at x=364635, y=-294577
+Sensor at x=3229566, y=1694167: closest beacon is at x=2827226, y=1579510
+Sensor at x=1600637, y=3984884: closest beacon is at x=955472, y=3457514
+Sensor at x=2959765, y=2820860: closest beacon is at x=2491502, y=2897876
+Sensor at x=2235330, y=3427797: closest beacon is at x=2491502, y=2897876
+Sensor at x=2428996, y=210881: closest beacon is at x=2827226, y=1579510
+Sensor at x=369661, y=687805: closest beacon is at x=364635, y=-294577
+Sensor at x=3558476, y=2123614: closest beacon is at x=4305648, y=2127118
+Sensor at x=3551529, y=2825104: closest beacon is at x=3696221, y=3226373
+Sensor at x=64895, y=3577: closest beacon is at x=364635, y=-294577
+Sensor at x=3079531, y=1538659: closest beacon is at x=2827226, y=1579510

day15/sample

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+Sensor at x=2, y=18: closest beacon is at x=-2, y=15
+Sensor at x=9, y=16: closest beacon is at x=10, y=16
+Sensor at x=13, y=2: closest beacon is at x=15, y=3
+Sensor at x=12, y=14: closest beacon is at x=10, y=16
+Sensor at x=10, y=20: closest beacon is at x=10, y=16
+Sensor at x=14, y=17: closest beacon is at x=10, y=16
+Sensor at x=8, y=7: closest beacon is at x=2, y=10
+Sensor at x=2, y=0: closest beacon is at x=2, y=10
+Sensor at x=0, y=11: closest beacon is at x=2, y=10
+Sensor at x=20, y=14: closest beacon is at x=25, y=17
+Sensor at x=17, y=20: closest beacon is at x=21, y=22
+Sensor at x=16, y=7: closest beacon is at x=15, y=3
+Sensor at x=14, y=3: closest beacon is at x=15, y=3
+Sensor at x=20, y=1: closest beacon is at x=15, y=3

day15/sol.py

@@ -0,0 +1,70 @@
+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)
+#print(data)
+
+none = set()
+
+Y = 10
+Y = 2000000
+
+for sx,sy,bx,by in data:
+    dx = abs(sx-bx)
+    dy = abs(sy-by)
+    dist = dx+dy
+    y = Y-sy
+    #for x in range(-dist,dist+1):
+    #    if abs(x)+abs(y) <= dist:
+    #        p = (sx+x, sy+y)
+    #        if p != (bx,by):
+    #            none.add(sx+x)
+
+print(len(none))
+
+objs = []
+for sx,sy,bx,by in data:
+    dist = abs(sx-bx) + abs(sy-by)
+    objs.append((sx,sy,dist))
+
+# find the closest sensor to x,y within dist
+def mindist(x,y, objs=objs):
+    for sx,sy,dist in yobjs:
+        d = abs(x-sx) + abs(y-sy)
+        if d <= dist:
+            yield dist-d
+
+# y=2573243
+Y = 2500000
+Y = 0
+
+objs.sort()
+
+for y in range(Y, 4000000+1):
+    ranges = []
+    for sx,sy,dist in objs:
+        dy = abs(y-sy)
+        if dy <= dist:
+            dx = dist - dy
+            ranges.append((sx-dx,sx+dx))
+    ranges.sort()
+    x = 0
+    for a,b in ranges:
+        if b < x:
+            continue
+        if x < a:
+            print(x,y,"=",x*4000000+y)
+            break
+        x = b+1
+        if x > 4000000:
+            break
+        #try:
+        #    d = max(mindist(x,y,objs=yobjs))
+        #    x += d+1
+        #except ValueError:
+        #    print(x,y)
+        #    break
+    if y % 100000 == 0:
+        print(y)
+