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Fix incorrect Manhattan distance calculation for custom goal states #3050

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Merged
merged 1 commit into from
Nov 18, 2025
Merged

Fix incorrect Manhattan distance calculation for custom goal states #3050

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11 changes: 8 additions & 3 deletions 8_puzzle.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,15 +26,20 @@ def priority(self) -> int:
return self.moves + self.manhattan()

def manhattan(self) -> int:
"""Calculate Manhattan distance from current to goal state."""
"""Calculate Manhattan distance using actual goal positions."""
distance = 0
# Create a lookup table for goal tile positions
goal_pos = {self.goal[i][j]: (i, j) for i in range(3) for j in range(3)}

for i in range(3):
for j in range(3):
if self.board[i][j] != 0:
x, y = divmod(self.board[i][j] - 1, 3)
value = self.board[i][j]
if value != 0: # skip the empty tile
x, y = goal_pos[value]
distance += abs(x - i) + abs(y - j)
return distance


def is_goal(self) -> bool:
"""Check if current state matches goal."""
return self.board == self.goal
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