如何使用一个类来存储在不同函数中更新的变量，然后在不同的函数中调用这些更新的变量？

Question

我正在解决一个涉及遍历n x m matrix以之字形方式的问题，其中n and m可以是相同的数字或不同的数字，即我们将有正方形或矩形矩阵。

为了解决这个问题，我有一个ma​​in方法，它会遍历矩阵；在这个主方法中，我创建并调用moveDiagonallyUpwards 和moveDiagonallyDownwards 方法以曲折的方式移动。

我遇到的问题是，当我将 row 和 col 作为参数从 main 方法传递给这两个其他方法时，在这些方法中我更新 row 和 col，例如+=1 或 -= 1。 当我返回主方法时，这些更改不会反映在主方法中。我也明白为什么会这样。

所以我的挑战是，如何将更新后的row 和col 传回主方法？我想过使用global class 来实现上述目的。 我的想法是创建一个单独的类来保存这些变量，如下所示，但我在 ma​​in 方法中调用和使用这些 global row and col 时遇到问题。

任何想法如何调整 ma​​in 方法 中的row and col 以实现上述目标？谢谢！

array = [
    [1, 3, 4, 10],
    [2, 5, 9, 11],
    [6, 8, 12, 15],
    [7, 13, 14, 16]
  ]

class matrixMovement: 
    def __init__(self,row=0,col=0,output=[]): 
        self.row = row
        self.col = col
        self.output = output
#Main Method
def zigzagTraverse(array):
    output.append(array[row][col])
    while array.row<= len(array)-1 or array.col<= len(array[0])-1: 
        if array.row< len(array)-1: 
            array.row += 1
            output.append(array[row][col])
            diagonalUp(row,col,array,output)
        if col < len(array[0])-1: 
            col += 1
            output.append(array[row][col])
            diagonalDown(row,col,array,output)
    return output
            
def diagonalUp(row,col,array,output): 
    while row > 0 and col< len(array[0])-1: 
        row -= 1
        col += 1
        output.append(array[row][col])
    return matrixMovemenet(row,col,output)
    
def diagonalDown(row,col,array,output): 
    while row<len(array)-1 and col > 0: 
        col-= 1
        row += 1
        output.append(array[row][col])
    return matrixMovemenet(row,col,output)

Answer 1

你有几个问题。一是局部范围。另一种是使用return 语句，但对返回的对象不做任何事情。

有几种方法可以解决这个问题。一种是忽略局部变量，只从matrixMovement 创建一个对象，并利用它是可变的这一事实。

class MatrixMovement: 
    def __init__(self, row=0, col=0, output=None):
        # I modified this to avoid the mutable default
        if output is None:
            output = []
        self.row = row
        self.col = col
        self.output = output


# Main Method
def zigzag_traverse(array):
    # this is the object we will be mutating
    obj = MatrixMovement()
    obj.output.append(array[obj.row][obj.col])
    while obj.row <= len(array) - 1 or obj.col <= len(array[0]) - 1: 
        if obj.row < len(array) - 1: 
            obj.row += 1
            obj.output.append(array[obj.row][obj.col])
            diagonal_up(obj, array)
        if obj.col < len(array[0]) - 1: 
            obj.col += 1
            obj.output.append(array[obj.row][obj.col])
            diagonal_down(obj, array)
        # without this condition the loop will never break
        if obj.row == len(array) - 1 and obj.col == len(array[0]) - 1:
            break
    return obj.output


def diagonal_up(obj, array):
    # since we are passing in a mutable object
    # anything attribute we change on it
    # will be reflected on the object from the call site
    while obj.row > 0 and obj.col < len(array[0]) - 1: 
        obj.row -= 1
        obj.col += 1
        obj.output.append(array[obj.row][obj.col])


def diagonal_down(obj, array):
    # the same rules as diagonal_up
    while obj.row < len(array) - 1 and obj.col > 0: 
        obj.col -= 1
        obj.row += 1
        obj.output.append(array[obj.row][obj.col])

Answer 2

在解决了我在您的遍历中发现的一些错误之后，我选择使用文档、边界检查来编写此代码。

解释是用 cmets 写的。有什么不懂的欢迎追问。

from typing import TypeVar, Sequence, TypeAlias

from dataclasses import dataclass

_T = TypeVar("_T")

MatrixType = Sequence[Sequence[_T]]

@dataclass
class Point:
    row: int
    col: int

def zigzag_traverse(matrix: MatrixType[_T]) -> list[_T]:
    output: list[_T] = []

    row_length = len(matrix[0])
    if any(len(row) != row_length for row in matrix):
        raise ValueError("Matrix is not rectangular.")
    
    # Initialize.
    boundry = Point(len(matrix) - 1, row_length - 1)
    
    if boundry.row < 0 or boundry.col < 0:
        return output  # Matrix is empty.

    pointer = Point(0, 0)


    # Start traversing.

    output.append(matrix[pointer.row][pointer.col])
    
    
    while pointer != boundry:

        # Go right until edge, then start moving down.
        if pointer.col < boundry.col:
            pointer.col += 1
        else:
            pointer.row += 1

        output.extend(_diagonal_left_down(pointer, matrix))

        # We reached the boundry, stop traversing.
        if pointer == boundry:
            break

        # Go down until edge, then start moving right.
        if pointer.row < boundry.row:
            pointer.row += 1
        else:
            pointer.col += 1

        output.extend(_diagonal_right_up(pointer, matrix))
    
    return output

def _diagonal_left_down(pointer: Point, matrix: MatrixType[_T]) -> list[_T]:
    """Traverse left-down diagonal.
    
    Args:
        pointer: The current position. Will be modified.
        matrix: The matrix to move over.
    
    Returns:
        The list of elements traversed.
    """
    row, col = pointer.row, pointer.col
    output = []

    while row < len(matrix) - 1 and col > 0:
        output.append(matrix[row][col])
        row += 1
        col -= 1
    
    # Reached the edge
    output.append(matrix[row][col])
    pointer.row, pointer.col = row, col

    return output

def _diagonal_right_up(pointer: Point, matrix: MatrixType[_T]) -> list[_T]:
    """Traverse right-up diagonal.
    
    Args:
        pointer: The current position. Will be modified.
        matrix: The matrix to move over.
    
    Returns:
        The list of elements traversed.
    """
    row, col = pointer.row, pointer.col
    output = []

    while row > 0 and col < len(matrix[0]) - 1:
        output.append(matrix[row][col])
        row -= 1
        col += 1
    
    # Reached the edge
    output.append(matrix[row][col])
    pointer.row, pointer.col = row, col

    return output