1225. Island Perimeter

描述

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.

您在真实的面试中是否遇到过这个题？   是

样例

[[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:

我用了最粗暴的办法，依次遍历，然后依据条件判断边。

class Solution {
public:
    /**
     * @param grid: a 2D array
     * @return: the perimeter of the island
     */
    int islandPerimeter(vector<vector<int>> &grid) {
        // Write your code here
        int result=0;
        for(int i=0;i<grid.size();i++){
            for(int j=0;j<grid[0].size();j++){
                if(grid[i][j]==1){
                    if(i==0||grid[i-1][j]==0) result++;
                    if(i==grid.size()-1||grid[i+1][j]==0) result++;
                    if(j==0||grid[i][j-1]==0) result++;
                    if(j==grid[0].size()-1||grid[i][j+1]==0) result++;
                }
            }
        }
        return result;
    }
};