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1162. As Far from Land as Possible (Medium)

Given an N x N grid containing only values 0 and 1, where 0 represents water and 1 represents land, find a water cell such that its distance to the nearest land cell is maximized and return the distance.

The distance used in this problem is the Manhattan distance: the distance between two cells (x0, y0) and (x1, y1) is |x0 - x1| + |y0 - y1|.

If no land or water exists in the grid, return -1.

 

Example 1:

Input: [[1,0,1],[0,0,0],[1,0,1]]
Output: 2
Explanation: 
The cell (1, 1) is as far as possible from all the land with distance 2.

Example 2:

Input: [[1,0,0],[0,0,0],[0,0,0]]
Output: 4
Explanation: 
The cell (2, 2) is as far as possible from all the land with distance 4.

 

Note:

1. 1 <= grid.length == grid[0].length <= 100
2. grid[i][j] is 0 or 1

Related Topics

[Breadth-first Search] [Graph]

Similar Questions

1. Shortest Distance from All Buildings (Hard)

Hints

Hint 1

Can you think of this problem in a backwards way ?

Hint 2

Imagine expanding outward from each land cell. What kind of search does that ?

Hint 3

Use BFS starting from all land cells in the same time.

Hint 4

When do you reach the furthest water cell?