广度优先搜索比预期结果少一个索引

如何解决广度优先搜索比预期结果少一个索引

我正在尝试在Python中实现面包优先搜索算法，以找到从矩阵（二维列表）左上角到数字9（无论它可能落在矩阵中的何处）的最短路径。由于某种原因，当我使用随附的print语句运行下面的代码时，我的x坐标将正确输出（到达索引5相对于期望的5）。但是，我的y坐标仍然短一个索引（例如，需要7，它停在6）。另外，当我打印队列时，它不是空的，但是由于某种原因该函数仍然结束。因此，我不明白为什么如果没有两个条件都满足（即队列为空或找到我们想要的坐标），为什么退出代码。

import numpy as np
from collections import deque


def shortest_path(maze):
    num_rows = len(maze)
    num_cols = len(maze[0])

row_moves = [1,-1,0]
col_moves = [0,1,-1]

# Convert maze to an array and use numpy to find coordinates of our goal,which is the 9.
maze_to_matrix = np.array(maze)
destination = np.where(maze_to_matrix == 9)
destination_x,destination_y = destination[1][0],destination[0][0]

def is_valid_move(matrix,visited,y,x):
    return (y >= 0) and (y < num_rows) and (x >= 0) and (x < num_cols) \
           and matrix[y][x] == 1 and not visited[y][x]


def bfs(matrix,dest_y,dest_x):

    # Construct matrix to keep track of visited cells.
    visited = [[False for x in range(num_cols)] for y in range(num_rows)]

    # Mark our origin as visited.
    # Our origin is always the top left node.
    visited[0][0] = True

    # Create an empty queue to keep track of our nodes to visit.
    queue = deque()

    # Append our starting coordinates and its minimum distance from the source to our queue.
    # First number is y coordinate,or outer list index.
    # Second number is x coordinate,or inner list index.
    queue.append((0,0))

    # Store the length of the longest path from source to destination
    min_dist = float('inf')

    # Pull most recently visited node off queue and determine if neighbouring
    # nodes are accessible. Continue until no valid unvisited nodes remain.
    while queue:
        (y,x,dist) = queue.popleft()
        print(f'y: {y} and dest_y: {dest_y}')
        print(f'x: {x} and dest_x: {dest_x}')

        # If our destination is found then break the loop and return value.
        if y == dest_y and x == dest_x:
            min_dist = dist
            break

        # Check for all possible movement directions from current (x,y)
        # and add valid movements to our queue.
        for i in range(4):
            if is_valid_move(matrix,y + row_moves[i],x + col_moves[i]):
                visited[y + row_moves[i]][x + col_moves[i]] = True
                queue.append((y + row_moves[i],x + col_moves[i],dist + 1))
                print(queue)

    if min_dist != float('inf'):
        return min_dist
    else:
        return "Desired destination can't be reached from given origin points."

return bfs(maze,destination_y,destination_x)


maze = [
    [1,0],[1,[0,9,0]
]

print(shortest_path(maze))

# Outputting y: 6 and dest_y: 7 x: 5 and dest_x: 5 and the queue is full.

解决方法

没关系，我是个白痴……在我的is_valid_move函数中，我只计算矩阵中值为1的空间，这意味着我们的目标9永远无效。

所以is_valid_function应该看起来像这样：

return (y >= 0) and (y < num_rows) and (x >= 0) and (x < num_cols) \
           and (matrix[y][x] == 1 or matrix[y][x] == 9) and not visited[y][x]