如何将python列表动态传递给另一个python-fi

Question

我正在用pygame开发一个N-Queen模拟程序。在

class NQ:

    def __init__(self,n):
        self.size = n
        self.columns = [] * self.size
        self.places = 0
        self.backtracks = 0

    def place(self, startRow=0): 
        if len(self.columns) == self.size:

            return self.columns


        else:
            for row in range(startRow, self.size): 
                if self.isSafe(len(self.columns), row) is True: 
                    self.columns.append(row)
                    self.places += 1 
                    return self.place()

            else: 
                lastRow = self.columns.pop()
                self.backtracks += 1 
                return self.place(startRow=lastRow + 1)

    def isSafe(self, col, row): 
        for threatRow in self.columns: 
            threatCol = self.columns.index(threatRow) 
            if row == threatRow or col == self.columns.index(threatRow):
                return False 
            elif threatRow + threatCol == row + col or threatRow - threatCol == row - col:
                return False 
        return True

    def process(n):

        nqueens = NQ(n)
        nqueens.place(0)
        return nqueens.columns

作为另一个棋盘输入程序，它们也相应地作为一个棋盘输入。 如果我想显示皇后区的移动，如何从递归code过程动态传递列表，以便可以看到确切的回溯过程。 谢谢你

Answer 1

如果你想知道递归函数内部发生了什么，你可以添加外部函数作为参数，然后你可以在递归内部使用它来打印算法的当前状态或在棋盘上画皇后。在

在示例中，我使用show_colums()在每次self.place()运行时打印self.columns。在

文件：不合格品在

class NQ:

    def __init__(self,n, callback): # added callback
        self.size = n
        self.columns = []
        self.places = 0
        self.backtracks = 0
        self.callback = callback # added callback

    def place(self, startRow=0): 

        self.callback(self.columns) # added callback

        if len(self.columns) == self.size:

            return self.columns

        else:
            for row in range(startRow, self.size): 
                if self.isSafe(len(self.columns), row) is True: 
                    self.columns.append(row)
                    self.places += 1 
                    return self.place()

            else: 
                lastRow = self.columns.pop()
                self.backtracks += 1 
                return self.place(startRow=lastRow + 1)

    def isSafe(self, col, row): 
        for threatRow in self.columns: 
            threatCol = self.columns.index(threatRow) 
            if row == threatRow or col == self.columns.index(threatRow):
                return False 
            elif threatRow + threatCol == row + col or threatRow - threatCol == row - col:
                return False 
        return True

文件：主.py在

^{pr2}$

部分结果

columns: []
columns: [0]
columns: [0, 2]
columns: [0, 2, 4]
columns: [0, 2, 4, 1]
columns: [0, 2, 4, 1, 3]
columns: [0, 2, 4, 1]
columns: [0, 2, 4, 1, 7]
columns: [0, 2, 4, 1]