import 2021

2021/day7/day7.py

@@ -0,0 +1,33 @@
+from collections import OrderedDict
+
+def part1(crabs):
+    moves = OrderedDict()
+    for pos in range(min(crabs), max(crabs) + 1):
+        # calculate total fuel required to move to pos:
+        for crab in crabs:
+            fuel_cost = abs(pos - crab)
+            moves[pos] = moves.get(pos, 0) + fuel_cost
+
+    min_move = min(moves, key=moves.get)
+    print(f"Part 1, min move {min_move}, cost {moves[min_move]}")
+
+def part2(crabs):
+    moves = OrderedDict()
+    for pos in range(min(crabs), max(crabs) + 1):
+        # calculate total fuel required to move to pos:
+        for crab in crabs:
+            dx = abs(pos - crab)
+            # S = (n+1)(u0 + un)/2
+            fuel_cost = dx * (dx+1)//2
+            moves[pos] = moves.get(pos, 0) + fuel_cost
+
+    min_move = min(moves, key=moves.get)
+    print(f"Part 1, min move {min_move}, cost {moves[min_move]}")
+
+
+if __name__ == "__main__":
+    with open("input.txt") as infile:
+        crabs = [int(x) for x in infile.readline().split(",")]
+    part1(crabs)
+    part2(crabs)
+