Package g0801_0900.s0807_max_increase_to_keep_city_skyline

Class Solution

java.lang.Object
g0801_0900.s0807_max_increase_to_keep_city_skyline.Solution
public class Solution extends java.lang.Object
807 - Max Increase to Keep City Skyline.

Medium

There is a city composed of n x n blocks, where each block contains a single building shaped like a vertical square prism. You are given a 0-indexed n x n integer matrix grid where grid[r][c] represents the height of the building located in the block at row r and column c.

A city’s skyline is the the outer contour formed by all the building when viewing the side of the city from a distance. The skyline from each cardinal direction north, east, south, and west may be different.

We are allowed to increase the height of any number of buildings by any amount (the amount can be different per building). The height of a 0-height building can also be increased. However, increasing the height of a building should not affect the city’s skyline from any cardinal direction.

Return the maximum total sum that the height of the buildings can be increased by without changing the city’s skyline from any cardinal direction.

Example 1:

Input: grid = [[3,0,8,4],[2,4,5,7],[9,2,6,3],[0,3,1,0]]

Output: 35

Explanation: The building heights are shown in the center of the above image.

The skylines when viewed from each cardinal direction are drawn in red.

The grid after increasing the height of buildings without affecting skylines is:

 gridNew = [ [8, 4, 8, 7], 
             [7, 4, 7, 7], 
             [9, 4, 8, 7],  
             [3, 3, 3, 3] ]

Example 2:

Input: grid = [[0,0,0],[0,0,0],[0,0,0]]

Output: 0

Explanation: Increasing the height of any building will result in the skyline changing.

Constraints:

  • n == grid.length
  • n == grid[r].length
  • 2 <= n <= 50
  • 0 <= grid[r][c] <= 100

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    maxIncreaseKeepingSkyline(int[][] grid)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • maxIncreaseKeepingSkyline

      public int maxIncreaseKeepingSkyline(int[][] grid)