463. Island Perimeter

xiaoxiao2021-02-27  1.0K+

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.


[[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: 方法1:我的解法,对于每一个岛屿方格,判断其周围的水的数目,特殊情况是行或列为零的情况和只有一行或一列的情况。

class Solution { public: int islandPerimeter(vector<vector<int>>& grid) { int row=grid.size(); int col=grid[0].size(); int sum=0; for(int i=0;i<row;i++) for(int j=0;j<col;j++) { if(grid[i][j]==1) sum+=dodo(grid,i,j,row,col); } return sum; } int dodo(vector<vector<int>>&grid,int i,int j,const int row,const int col) { int n=0; if(i==0||i==row-1) n++; if(row-1==0) n++; if(j==0||j==col-1) n++; if(col-1==0) n++; if(i>=1&&grid[i-1][j]==0) n++; if(j>=1&&grid[i][j-1]==0) n++; if(i<row-1&&grid[i+1][j]==0) n++; if(j<col-1&&grid[i][j+1]==0) n++; return n; } };方法2:每个方格周长为4,如果有相邻,则减1.

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