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Given a m * n grid, where each cell is either 0 (empty) or 1 (obstacle). In one step, you can move up, down, left or right from and to an empty cell.
Return the minimum number of steps to walk from the upper left corner (0, 0) to the lower right corner (m-1, n-1) given that you can eliminate at mostk obstacles. If it is not possible to find such walk return -1.
Example 1:
Input:
grid =
[[0,0,0],
[1,1,0],
[0,0,0],
[0,1,1],
[0,0,0]],
k = 1
Output: 6
Explanation:
The shortest path without eliminating any obstacle is 10.
The shortest path with one obstacle elimination at position (3,2) is 6. Such path is (0,0) -> (0,1) -> (0,2) -> (1,2) -> (2,2) -> (3,2) -> (4,2).
Example 2:
Input:
grid =
[[0,1,1],
[1,1,1],
[1,0,0]],
k = 1
Output: -1
Explanation:
We need to eliminate at least two obstacles to find such a walk.
Shortest Path in a Grid with Obstacles Elimination
Given a
m * n
grid, where each cell is either0
(empty) or1
(obstacle). In one step, you can move up, down, left or right from and to an empty cell.Return the minimum number of steps to walk from the upper left corner
(0, 0)
to the lower right corner(m-1, n-1)
given that you can eliminate at mostk
obstacles. If it is not possible to find such walk return -1.Example 1:
Example 2:
Constraints:
grid.length == m
grid[0].length == n
1 <= m, n <= 40
1 <= k <= m*n
grid[i][j] == 0 **or** 1
grid[0][0] == grid[m-1][n-1] == 0
算法思路:利用
BFS
解题,将二维矩阵扩充为三维,z代表当前消除的障碍物数量;visited[x][y][z]
,代表消除z个障碍是否到达[x, y]
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