day 8, easy

d08/run.py

@@ -0,0 +1,49 @@
+import sys, os
+from collections import defaultdict as dd
+from itertools import combinations as comb
+
+def grid_geom(G):
+    H = len(G)
+    W = len(G[0])
+    return W, H
+
+def in_grid(G, x, y) -> bool:
+    W, H = grid_geom(G)
+    return x>=0 and x<W and y>=0 and y<H
+
+def get_in_grid(G, x, y):
+    if in_grid(G, x,y):
+        return G[y][x]
+
+R = list(range(50)) if len(sys.argv)>1 and sys.argv[1]=="2" else [1]
+
+L = sys.stdin.read().strip().split("\n")
+G = [list(l) for l in L]
+
+
+# dico of position
+P = dd(list)
+W, H = grid_geom(G)
+for y in range(H):  # rows
+    for x in range(W):  # cols
+        v = get_in_grid(G, x, y)
+        if v != '.':
+            P[v].append((x, y))
+
+A = set()  # antinodes
+for k,v in P.items():
+    for a,b in comb(v,2):
+        x1, y1 = a
+        x2, y2 = b
+        dx = x2 - x1
+        dy = y2 - y1
+        for i in R:
+            x3 = x1 - i*dx
+            y3 = y1 - i*dy
+            x4 = x2 + i*dx
+            y4 = y2 + i*dy
+            if in_grid(G, x3, y3):
+                A.add((x3,y3))
+            if in_grid(G, x4, y4):
+                A.add((x4,y4))
+print(len(A))