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:

大概意思就是求一個島的周長

思路如下，分四個邊處理，例如左邊的邊只有在最左邊或者左邊沒有島的時候可以算成周長，其余同理

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

463. Island Perimeter