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?微信公眾號：山青詠芝（shanqingyongzhi）
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?原文地址：https://www.cnblogs.com/strengthen/p/10345792.html?
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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:

Input: [[0,1,0,0],[1,1,1,0],[0,1,0,0],[1,1,0,0]]Output: 16Explanation: The perimeter is the 16 yellow stripes in the image below:

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給定一個包含 0 和 1 的二維網格地圖，其中 1 表示陸地?0 表示水域。

網格中的格子水平和垂直方向相連（對角線方向不相連）。整個網格被水完全包圍，但其中恰好有一個島嶼（或者說，一個或多個表示陸地的格子相連組成的島嶼）。

島嶼中沒有“湖”（“湖” 指水域在島嶼內部且不和島嶼周圍的水相連）。格子是邊長為 1 的正方形。網格為長方形，且寬度和高度均不超過 100 。計算這個島嶼的周長。?

示例 :

輸入: [[0,1,0,0],[1,1,1,0],[0,1,0,0],[1,1,0,0]]輸出: 16解釋: 它的周長是下面圖片中的 16 個黃色的邊：

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244ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 var landCount = 0 4 var neighborCount = 0 5 6 for i in 0..<grid.count { 7 for j in 0..<grid[i].count { 8 if grid[i][j] == 1 { 9 landCount += 1 10 if i < grid.count - 1 && grid[i + 1][j] == 1 { 11 neighborCount += 1 12 } 13 if j < grid[i].count - 1 && grid[i][j + 1] == 1 { 14 neighborCount += 1 15 } 16 } 17 } 18 } 19 20 return landCount * 4 - neighborCount * 2 21 } 22 }

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276ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 var count:Int = 0 4 for i in 0..<grid.count { 5 for j in 0..<grid[i].count{ 6 if(grid[i][j] == 1){ 7 count += 4; 8 } 9 if(grid[i][j] == 1 && i - 1 >= 0 && grid[i - 1][j] == 1){ 10 count -= 2; 11 } 12 if(grid[i][j] == 1 && j - 1 >= 0 && grid[i][j - 1] == 1){ 13 count -= 2; 14 } 15 } 16 } 17 return count 18 } 19 }

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504ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 var perimeter: Int = 0 4 for i in 0..<grid.count { 5 for j in 0..<grid[i].count { 6 if grid[i][j] == 1 { 7 var commonEdges = 0 8 9 if i > 0 && grid[i - 1][j] == 1 { 10 commonEdges += 1 11 } 12 if i < grid.count - 1 && grid[i + 1][j] == 1 { 13 commonEdges += 1 14 } 15 16 if j > 0 && grid[i][j - 1] == 1 { 17 commonEdges += 1 18 } 19 if j < grid[i].count - 1 && grid[i][j + 1] == 1 { 20 commonEdges += 1 21 } 22 23 perimeter += 4 - commonEdges 24 } 25 } 26 } 27 return perimeter 28 } 29 }

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528ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 var perimeterTotal = 0 4 if grid.count == 0 { 5 return 0 6 } 7 perimeterTotal = lrBoundTotal(grid) + tbBoundTotal(grid) 8 return perimeterTotal 9 } 10 11 func lrBoundTotal(_ grid:[[Int]]) -> Int { 12 let height = grid.count 13 let width = grid[0].count 14 var blockCount = 0 15 for i in 0..<height { 16 var emptyWater = 1 17 for j in 0..<width { 18 let val = grid[i][j] 19 if (val == 1) { 20 if (emptyWater == 1) { 21 blockCount += 1 22 } 23 emptyWater = 0 24 } else { 25 emptyWater = 1 26 } 27 } 28 } 29 return blockCount * 2 30 } 31 32 func tbBoundTotal(_ grid:[[Int]]) -> Int { 33 let height = grid.count 34 let width = grid[0].count 35 var blockCount = 0 36 for j in 0..<width { 37 var emptyWater = 1 38 for i in 0..<height { 39 let val = grid[i][j] 40 if (val == 1) { 41 if (emptyWater == 1) { 42 blockCount += 1 43 } 44 emptyWater = 0 45 } else { 46 emptyWater = 1 47 } 48 } 49 } 50 return blockCount * 2 51 } 52 }

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576ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 var matrix = grid 4 var perim = 0 5 for i in 0..<grid.count{ 6 for j in 0..<grid[0].count{ 7 if grid[i][j] == 1{ 8 perim += perime(&matrix, (i, j)) 9 } 10 } 11 } 12 return perim 13 } 14 15 func perime(_ grid: inout [[Int]], _ point: (Int, Int))->Int{ 16 var count = 0 17 if point.0 == 0{ 18 count += 1 19 }else{ 20 if grid[point.0 - 1][point.1] == 0{ 21 count += 1 22 } 23 } 24 25 if point.0 == grid.count - 1{ 26 count += 1 27 }else{ 28 if grid[point.0 + 1][point.1] == 0{ 29 count += 1 30 } 31 } 32 33 if point.1 == 0{ 34 count += 1 35 }else{ 36 if grid[point.0][point.1 - 1] == 0{ 37 count += 1 38 } 39 } 40 41 if point.1 == grid[0].count - 1{ 42 count += 1 43 }else{ 44 if grid[point.0][point.1 + 1] == 0{ 45 count += 1 46 } 47 } 48 return count 49 } 50 }

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624ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 let rows = grid.count 4 let cols = grid[0].count 5 var sum = 0 6 for i in 0...rows-1 7 { 8 for j in 0...cols-1 9 { 10 if grid[i][j] == 1 11 { 12 if (i-1 >= 0 && grid[i-1][j] == 0) || i-1 < 0 { 13 sum += 1 14 } 15 if (i+1 < rows && grid[i+1][j] == 0) || i+1 == rows{ 16 sum += 1 17 } 18 if (j-1 >= 0 && grid [i][j-1] == 0) || j-1 < 0{ 19 sum += 1 20 } 21 if (j+1 < cols && grid[i][j+1] == 0) || j+1 == cols{ 22 sum += 1 23 } 24 } 25 } 26 } 27 return sum 28 } 29 }

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648ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 if grid.isEmpty || grid[0].isEmpty {return 0} 4 var res:Int = 0 5 var m:Int = grid.count 6 var n:Int = grid[0].count 7 for i in 0..<m 8 { 9 for j in 0..<n 10 { 11 if grid[i][j] == 0 12 { 13 continue 14 } 15 res += 4 16 if i > 0 && grid[i - 1][j] == 1 17 { 18 res -= 2 19 } 20 if j > 0 && grid[i][j - 1] == 1 21 { 22 res -= 2 23 } 24 } 25 } 26 return res 27 } 28 }

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964ms

1 class Solution { 2 func islandPerimeter(_ grid: [[Int]]) -> Int { 3 var sum = 0 4 for i in 0..<grid.count { 5 let g = grid[i] 6 for x in 0..<g.count{ 7 let top = i-1 < 0 ? 0 : grid[i-1][x] 8 let left = x-1 < 0 ? 0 :g[x-1] 9 let bottom = i+1 >= grid.count ? 0 : grid[i+1][x] 10 let right = x+1 >= g.count ? 0 :g[x+1] 11 let z = g[x] 12 13 if z == 1{ 14 sum = sum + 4 - (top + left + bottom + right) 15 } 16 } 17 } 18 return sum 19 } 20 }

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轉載于:https://www.cnblogs.com/strengthen/p/10345792.html

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