Count Covered Buildings
You are given a positive integer n, representing an n x n city. You are also given a 2D grid buildings, where buildings[i] = [x, y] denotes a unique building located at coordinates [x, y].
A building is covered if there is at least one building in all four directions: left, right, above, and below.
Return the number of covered buildings.
Example 1
Input
n = 3, buildings = [[1,2],[2,2],[3,2],[2,1],[2,3]]Output
1Only building
[2,2] is covered because it has at least one building above, below, left, and right.Example 2
Input
n = 3, buildings = [[1,1],[1,2],[2,1],[2,2]]Output
0No building has at least one building in all four directions.
Constraints
- 2 <= n <= 10^5
- 1 <= buildings.length <= 10^5
- buildings[i] = [x, y]
- 1 <= x, y <= n
- All coordinates of
buildingsare unique.