<leetcode>463. Island Perimeter

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本文介绍了一种通过遍历二维数组来计算岛屿周长的方法。针对一个由1和0组成的地图，1代表陆地，0代表水域，算法遍历每个单元格，计算陆地的周长并考虑相邻陆地的影响。

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463. 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:

题目大意：

用一个数组表示上图的地图，其中1表示陆地，0表示水。求陆地的周长

思路：

遍历整个数组，是陆地的周长+4，上下左右有陆地的话，减1

class Solution {
    public int islandPerimeter(int[][] grid) {
        //int[][] grid = {{0,1,0,0},
                //{1,1,1,0},
                //{0,1,0,0},
                //{1,1,0,0}};
        int count = 0;
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[i].length; j++) {
                 if(grid[i][j]==1){
                     count+=4;
                     if((i-1>=0)&&(grid[i-1][j]==1)) count--;
                     if(i+1<=grid.length-1&&(grid[i+1][j]==1)) count--;
                     if(j+1<=grid[i].length-1&&(grid[i][j+1]==1)) count --;
                     if((j-1>=0)&&(grid[i][j-1]==1)) count--;
                 }
            }
        }
        //System.out.println(count);
        return count;
    }
}