1 package Today;
2 //LeetCode:463. Island Perimeter
3 /*
4 You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water.
5 Grid cells are connected horizontally/vertically (not diagonally).
6 The grid is completely surrounded by water, and there is exactly one island
7 (i.e., one or more connected land cells). The island doesn't have "lakes"
8 (water inside that isn't connected to the water around the island).
9 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.
10
11 Example:
12
13 [[0,1,0,0],
14 [1,1,1,0],
15 [0,1,0,0],
16 [1,1,0,0]]
17
18 Answer: 16
19 Explanation: The perimeter is the 16 yellow stripes in the image below:
20
21 */
22 public class islandPerimeter463 {
23 public static int islandPerimeter(int[][] grid) {
24 int count=0;
25 for(int i=0;i<grid.length;i++){
26 for(int j=0;j<grid[i].length;j++){
27 if(grid[i][j]==1){
28 count+=4;
29 if(j>0&&grid[i][j-1]==1)
30 count--;
31 if(j<grid[i].length-1&&grid[i][j+1]==1)
32 count--;
33 if(i>0&&grid[i-1][j]==1)
34 count--;
35 if(i<grid.length-1&&grid[i+1][j]==1)
36 count--;
37 }
38 }
39 }
40 return count;
41 }
42 //study 其实只要考虑右边和下面的情况就可以了，count=count-2;
43
44 public static void main(String[] args) {
45 // TODO Auto-generated method stub
46 int[][] grid={{0,1,0,0},{1,1,1,0},{0,1,0,0},{1,1,0,0}};
47 System.out.println(islandPerimeter(grid));
48
49 }
50
51 }
