[Swift]LeetCode695. 岛屿的最大面积 | Max Area of Island

it2022-05-06 1

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Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

Find the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)

Example 1:

[[0,0,1,0,0,0,0,1,0,0,0,0,0], [0,0,0,0,0,0,0,1,1,1,0,0,0], [0,1,1,0,1,0,0,0,0,0,0,0,0], [0,1,0,0,1,1,0,0,1,0,1,0,0], [0,1,0,0,1,1,0,0,1,1,1,0,0], [0,0,0,0,0,0,0,0,0,0,1,0,0], [0,0,0,0,0,0,0,1,1,1,0,0,0], [0,0,0,0,0,0,0,1,1,0,0,0,0]]

Given the above grid, return 6. Note the answer is not 11, because the island must be connected 4-directionally.

Example 2:

[[0,0,0,0,0,0,0,0]]

Given the above grid, return 0.

Note: The length of each dimension in the given grid does not exceed 50.

给定一个包含了一些 0 和 1的非空二维数组 grid , 一个岛屿是由四个方向 (水平或垂直) 的 1 (代表土地) 构成的组合。你可以假设二维矩阵的四个边缘都被水包围着。

找到给定的二维数组中最大的岛屿面积。(如果没有岛屿，则返回面积为0。)

示例 1:

对于上面这个给定矩阵应返回 6。注意答案不应该是11，因为岛屿只能包含水平或垂直的四个方向的‘1’。

示例 2:

[[0,0,0,0,0,0,0,0]]

对于上面这个给定的矩阵, 返回 0。

注意: 给定的矩阵grid 的长度和宽度都不超过 50。

Runtime: 76 ms Memory Usage: 20 MB 1 class Solution { 2 func maxAreaOfIsland(_ grid: [[Int]]) -> Int { 3 var tempGrid = grid 4 var area = 0 5 let m = tempGrid.count 6 var n = 0 7 var islandMax = 0 8 for i in 0..<m { 9 n = tempGrid[i].count 10 for j in 0..<n { 11 area = 0 12 area = dfs(i, j, m, n, &tempGrid, &area) 13 islandMax = max(islandMax, area) 14 } 15 } 16 return islandMax 17 } 18 19 func dfs(_ i: Int,_ j: Int,_ m: Int,_ n:Int,_ grid: inout [[Int]],_ tempArea: inout Int) -> Int { 20 if i<0 || i>=m || j<0 || j>=n || grid[i][j] == 0 { 21 return tempArea 22 } 23 grid[i][j] = 0 24 tempArea += 1 25 tempArea = dfs(i+1, j, m, n, &grid, &tempArea) 26 tempArea = dfs(i-1, j, m, n, &grid, &tempArea) 27 tempArea = dfs(i, j+1, m, n, &grid, &tempArea) 28 tempArea = dfs(i, j-1, m, n, &grid, &tempArea) 29 return tempArea 30 } 31 }

80ms

1 class Solution { 2 func maxAreaOfIsland(_ grid: [[Int]]) -> Int { 3 var dp:[[Int]] = grid 4 var mX: Int = 0 5 6 for i in 0 ..< dp.count { 7 for j in 0 ..< dp[0].count { 8 // print("i:\(i) j:\(j)") 9 if dp[i][j] == 1 { 10 mX = max(mX, area(&dp,i,j)) 11 } 12 } 13 } 14 15 return mX 16 } 17 18 func area(_ dp: inout [[Int]], _ i:Int, _ j:Int) -> Int { 19 if i < dp.count && i >= 0 && j < dp[0].count && j >= 0 && dp[i][j] == 1 { 20 dp[i][j] = 0 21 return 1 + area(&dp, i-1, j) + area(&dp, i+1, j) + area(&dp, i, j-1) + area(&dp, i, j+1) 22 } 23 return 0 24 } 25 }

92ms

1 class Solution { 2 var height = 0 3 var width = 0 4 5 var grid: [[Int]]! 6 var visited: [[Bool]]! 7 8 func maxAreaOfIsland(_ grid: [[Int]]) -> Int { 9 height = grid.count 10 width = grid[0].count 11 12 self.grid = grid 13 14 var maxSize = 0 15 visited = Array(repeating:Array(repeating: false, count: width), count: height) 16 17 for y in 0..<grid.count { 18 for x in 0..<grid[0].count { 19 if grid[y][x] == 1 && visited[y][x] == false { 20 let size = visitIsland(x: x, y: y) 21 if size > maxSize { 22 maxSize = size 23 } 24 } 25 } 26 } 27 return maxSize 28 } 29 30 31 func visitIsland(x: Int, y: Int) -> Int { 32 // print("visit island x: \(x) y: \(y)") 33 if x < 0 || y < 0 || x >= width || y >= height { 34 return 0 35 } 36 if grid[y][x] == 0 || visited[y][x] == true { 37 return 0 38 } 39 visited[y][x] = true 40 var size = 1 41 size = size + visitIsland(x: x-1, y: y) 42 size = size + visitIsland(x: x+1, y: y) 43 size = size + visitIsland(x: x, y: y-1) 44 size = size + visitIsland(x: x, y: y+1) 45 return size 46 } 47 }

108ms

1 class Solution { 2 var maxCount = 0 3 let transform = [[0,1],[0,-1],[1,0],[-1,0]] 4 func maxAreaOfIsland(_ grid: [[Int]]) -> Int { 5 var grid = grid 6 for i in 0..<grid.count { 7 for j in 0..<grid[0].count { 8 if grid[i][j] == 1 { 9 let count = dfs(&grid, i, j) 10 if maxCount < count { 11 maxCount = count 12 } 13 } 14 } 15 } 16 return maxCount 17 } 18 19 func dfs(_ grid: inout [[Int]], _ x: Int, _ y: Int) -> Int { 20 if x >= 0 && x < grid.count && y >= 0 && y < grid[0].count && grid[x][y] == 1 { 21 grid[x][y] = 0 22 var count = 1 23 for i in 0..<4 { 24 let xx = x + transform[i][0] 25 let yy = y + transform[i][1] 26 count = count + dfs(&grid, xx, yy) 27 } 28 return count 29 } else { 30 return 0 31 } 32 } 33 }

108ms

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

112ms

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

132 ms

1 class Solution { 2 var dirs:[[Int]] = [[0,-1],[-1,0],[0,1],[1,0]] 3 func maxAreaOfIsland(_ grid: [[Int]]) -> Int { 4 var grid = grid 5 var m:Int = grid.count 6 var n:Int = grid[0].count 7 var res:Int = 0 8 for i in 0..<m 9 { 10 for j in 0..<n 11 { 12 if grid[i][j] != 1 13 { 14 continue 15 } 16 var cnt:Int = 0 17 var q:[(Int,Int)] = [(i,j)] 18 grid[i][j] *= -1 19 while (!q.isEmpty) 20 { 21 var t:(Int,Int) = q.first! 22 q.removeFirst() 23 cnt += 1 24 res = max(res, cnt) 25 for dir in dirs 26 { 27 var x:Int = t.0 + dir[0] 28 var y:Int = t.1 + dir[1] 29 if x < 0 || x >= m || y < 0 || y >= n || grid[x][y] <= 0 30 { 31 continue 32 } 33 grid[x][y] *= -1 34 q.append((x, y)) 35 } 36 } 37 } 38 } 39 return res 40 } 41 }

转载于:https://www.cnblogs.com/strengthen/p/10502593.html

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