【LeetCode】463. Island Perimeter

最新推荐文章于 2020-10-30 10:37:17 发布

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本文介绍了一种计算二维网格中岛屿周长的方法。该方法通过遍历每个单元格并检查其相邻单元格的状态来确定岛屿的边界，从而计算出岛屿的总周长。

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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:

/**
 * @param {number[][]} grid
 * @return {number}
 */
var islandPerimeter = function(grid) {
    var count = 0;
    for(var i=0;i<grid.length;i++){
        grid[i].push(0);
        grid[i].unshift(0);
    }
    var len=grid[0].length;
    grid.push((new Array(len)).fill(0));
    grid.unshift(new Array(len).fill(0))
    var len1=grid.length;
    var len2=grid[0].length;
    for(var i = 0 ; i < len1 ; i++){
        for(var j = 0 ; j<len2;j++){
            if(grid[i][j]===1){
                var temp=0;
                if(grid[i][j+1]===1){temp++;}
                if(grid[i][j-1]===1){temp++;}
                if(grid[i-1][j]===1){temp++;}
                if(grid[i+1][j]===1){temp++;}
                if(temp==0){count+=4;}
                else if(temp==1){count+=3;}
                else if(temp==2){count+=2;}
                else if(temp==3){count+=1;}
                
            }
        }
    }
    return count;
};

这题主要要多考虑边界值。