97 lines
3.1 KiB
Nim
97 lines
3.1 KiB
Nim
# Copyright 2022 Mattia Giambirtone & All Contributors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import game
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import util/matrix
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type
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Move = ref object
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## A specific state in a
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## tic-tac-toe match, with
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## all of its children states
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state: Matrix[int]
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# Since tic-tac-toe is a rather
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# simple game, we can generate all
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# possible (legal) board configurations
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# and then look up the current board when
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# playing against the user in order to find
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# the best move to win the match
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next: array[9, Move]
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parent: Move
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depth: int
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proc generateMoves*(map: Matrix[int], turn: TileKind, depth: int = 0): Move =
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## Generates the full tree of all
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## possible tic tac toe moves starting
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## from a given board state
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new(result)
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result.state = map.copy()
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result.depth = depth
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if result.state.asGame().get() != Playing:
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# The game is over, no need to generate
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# any more moves!
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return
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for row in 0..<map.shape.rows:
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for col in 0..<map.shape.cols:
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if TileKind(result.state[row, col]) == Empty:
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let index = row * map.shape.cols + col
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new(result.next[index])
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result.next[index].parent = result
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var copy = result.state.copy()
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copy[row, col] = turn.int()
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result.next[index] = generateMoves(copy, if turn == Self: Enemy else: Self, depth + 1)
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proc exists*(map: Matrix[int], tree: Move): int =
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## Returns the depth of a given move in
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## the solution tree. A return value of -1
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## indicates the move is illegal
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if all(map == tree.state):
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echo map.asGame()
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return tree.depth
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else:
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var i = 0
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var idx: tuple[row, col: int]
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while i < 9:
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idx = ind2sub(i, map.shape)
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if tree.next[i].isNil() or tree.next[i].state[idx.row, idx.col] != map[idx.row, idx.col]:
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inc(i)
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continue
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elif map.exists(tree.next[i]) != -1:
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return tree.next[i].depth
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inc(i)
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return -1
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proc print(self: Move) =
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## Traverses the move tree recursively
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## (meant for debugging)
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if self.isNil():
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return
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var board = self.state.asGame()
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echo board
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echo board.get(), "\n"
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for i in 0..<9:
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print(self.next[i])
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when isMainModule:
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var g = build(@[0, 0, 0, 0, 0, 0, 0, 0, 0])
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let m = generateMoves(g.map, Self)
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g = build(@[1, 1, 2, 2, 2, 1, 1, 2, 1])
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echo g.map.exists(m)
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g = build(@[1, 1, 2, 2, 2, 1, 1, 2, 2])
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echo g.map.exists(m)
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