2019-01-25 02:52:40 +08:00
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"""
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递归回溯法：叫称为试探法，按选优条件向前搜索，当搜索到某一步，
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发现原先选择并不优或达不到目标时，就退回一步重新选择。
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经典问题：骑士巡逻
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"""
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import os
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import sys
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import time
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SIZE = 5
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total = 0
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def print_board(board):
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# os.system('clear')
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for row in board:
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for col in row:
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print(str(col).center(4), end='')
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print()
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def patrol(board, row, col, step=1):
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if row >= 0 and row < SIZE and \
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col >= 0 and col < SIZE and \
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board[row][col] == 0:
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board[row][col] = step
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if step == SIZE * SIZE:
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global total
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total += 1
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print(f'第{total}种走法: ')
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print_board(board)
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patrol(board, row - 2, col - 1, step + 1)
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patrol(board, row - 1, col - 2, step + 1)
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patrol(board, row + 1, col - 2, step + 1)
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patrol(board, row + 2, col - 1, step + 1)
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patrol(board, row + 2, col + 1, step + 1)
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patrol(board, row + 1, col + 2, step + 1)
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patrol(board, row - 1, col + 2, step + 1)
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patrol(board, row - 2, col + 1, step + 1)
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board[row][col] = 0
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def main():
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board = [[0] * SIZE for _ in range(SIZE)]
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patrol(board, SIZE - 1, SIZE - 1)
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if __name__ == '__main__':
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main()
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