LeetCode 463. Island Perimeter

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本文介绍了一种通过逐个扫描二维网格来计算岛屿周长的方法。该算法适用于LeetCode上的一道题目，即给定一个由0和1组成的矩阵，1表示陆地，0表示水域，求岛屿的周长。

原题网址：https://leetcode.com/problems/island-perimeter/

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:

方法：逐个扫描。

public class Solution {
    public int islandPerimeter(int[][] grid) {
        int p = 0;
        for(int i = 0; i < grid.length; i++) {
            for(int j = 0; j < grid[i].length; j++) {
                if (grid[i][j] == 0) continue;
                if (i == 0 || grid[i - 1][j] == 0) p++;
                if (i == grid.length - 1 || grid[i + 1][j] == 0) p++;
                if (j == 0 || grid[i][j - 1] == 0) p++;
                if (j == grid[i].length - 1 || grid[i][j + 1] == 0) p++;
            }
        }
        return p;
    }
}