LeetCode Island Perimeter

Posted Dylan_Java_NYC

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了LeetCode Island Perimeter相关的知识,希望对你有一定的参考价值。

原题链接在这里:https://leetcode.com/problems/island-perimeter/

题目:

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells). The island doesn‘t have "lakes" (water inside that isn‘t connected to the water around the island). One cell is a square with side length 1. The grid is rectangular, width and height don‘t exceed 100. Determine the perimeter of the island.

Example:

[[0,1,0,0],
 [1,1,1,0],
 [0,1,0,0],
 [1,1,0,0]]

Answer: 16
Explanation: The perimeter is the 16 yellow stripes in the image below:

技术分享

题解:

land数目乘以4 -  border数目乘以2就是结果.

border数目通过检查当前land的右侧下侧是否为land得出。

Time Complexity: O(m*n), m = grid.length, n = grid[0].length.

Space: O(1).

AC Java:

 1 public class Solution {
 2     public int islandPerimeter(int[][] grid) {
 3         if(grid == null || grid.length == 0 || grid[0].length == 0){
 4             return 0;
 5         }
 6         int landNum = 0;
 7         int borderNum = 0;
 8         for(int i = 0; i<grid.length; i++){
 9             for(int j = 0; j<grid[0].length; j++){
10                 if(grid[i][j] == 1){
11                     landNum++;
12                     if(i<grid.length-1 && grid[i+1][j] == 1){
13                         borderNum++;
14                     }
15                     if(j<grid[0].length-1 && grid[i][j+1] == 1){
16                         borderNum++;
17                     }
18                 }
19             }
20         }
21         return landNum*4 - borderNum*2;
22     }
23 }

 

以上是关于LeetCode Island Perimeter的主要内容,如果未能解决你的问题,请参考以下文章

[LeetCode] Island Perimeter

[leetcode-463-Island Perimeter]

Leetcode-463 Island Perimeter

[LeetCode] 463 Island Perimeter

leetcode 463. Island Perimeter

leetcode算法:Island Perimeter