LeetCode-463. Island Perimeter (Java)

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:

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题目的意思是计算岛的周长，如果小岛（1）邻水（0），周长就加1，否则减1。我可能思路不对，想的过于复杂，半天没做出来，最后参考了下别人的代码LeetCode-463. Island Perimeter(Java)，自己学习一下。

public static int islandPerimeter(int[][] grid) {
int result = 0;
for(int i=0;i<grid.length;i++){
for(int j=0;j<grid[i].length;j++){
if(grid[i][j]==1){
//周长先加4，然后判断周围是水还是陆地
result+=4;
//如果不是第0行，则
if(i!=0){
//判断这个元素上一行的元素是不是陆地
if(grid[i-1][j]==1)
result--;
}
//如果不是第0个元素，则
if(j!=0){
//判断这个元素左边的元素是不是陆地
if(grid[i][j-1]==1)
result--;
}
//如果不是最后一行，则
if(i!=grid.length-1){
//判断这个元素下一行同列元素是不是陆地
if(grid[i+1][j]==1)
result--;
}
//如果不是第i行最后一个元素，则
if(j!=grid[i].length-1){
//判断i行第j+1个元素是不是陆地
if(grid[i][j+1]==1)
result--;
}
}
}
}
return result;
}