最近對算法突然來了興趣，奈何大學(xué)學(xué)的數(shù)據(jù)結(jié)構(gòu)算法已經(jīng)丟完了，只有自己一點點的撿回來啰。
言歸正傳，來看看LeetCode一道經(jīng)典題：島嶼的個數(shù)
此題可以使用BFS，DFS來解就可以了，我這里分別用了棧，隊列，遞歸三種方法來解，上代碼。

class Solution {
    

    var rows : Int!
    var cols : Int!
    var visited : [[Bool]]!
    var stack : [CGPoint] = []

    func numIslands(_ grid : [[Character]]) -> Int {
        if (grid.count == 0){
            return 0
        }
        var ans = 0
        rows = grid.count
        cols = grid[0].count
        visited = Array(repeating: Array(repeating: false, count: cols), count: rows)
        for i in 0..<rows {
            for j in 0..<cols{
                if (grid[i][j] == "1" && visited[i][j] == false ){
                    ans += 1
                    //BFS(getBFS: grid, i: i, j: j)    //遞歸
                    //BFSWithQueue(grid, i: i, j: j) //隊列
                    //stack = []
                    //DFSWithStack(grid, i: i, j: j) //棧
                }
                
            }
        }
        
        return ans
    }

    func BFS(getBFS grid : [[Character]], i : Int, j : Int){
        if(i>=0 && i<rows && j>=0 && j<cols){
            if(grid[i][j] == "1" && visited[i][j] == false){
                visited[i][j] = true
                BFS(getBFS: grid, i: i+1, j: j)
                BFS(getBFS: grid, i: i-1, j: j)
                BFS(getBFS: grid, i: i, j: j-1)
                BFS(getBFS: grid, i: i, j: j+1)
            }
        }
    }
    
    func BFSWithQueue(_ grid : [[Character]], i : Int, j : Int) {
        var queue : [CGPoint] = []
        queue.append(CGPoint.init(x: i, y: j))
        while !queue.isEmpty {
            let x = Int(queue.first!.x)
            let y = Int(queue.first!.y)

            if(x>=0 && x<rows && y>=0 && y<cols){
                if(grid[x][y] == "1" && visited[x][y] == false){
                    queue.append(CGPoint.init(x: x+1, y: y))
                    queue.append(CGPoint.init(x: x-1, y: y))
                    queue.append(CGPoint.init(x: x, y: y+1))
                    queue.append(CGPoint.init(x: x, y: y-1))
                    visited[x][y] = true;
                }
            }
            queue.removeFirst()
        }
    }
    
    func DFSWithStack(_ grid : [[Character]], i : Int, j : Int) {
        

        if(i>=0 && i<rows && j>=0 && j<cols ){
            stack.append(CGPoint.init(x: i, y: j))
            let x = Int(stack.last!.x)
            let y = Int(stack.last!.y)
            if(grid[x][y] == "0"  || visited[x][y] == true ){
            stack.removeLast()
            return;
            }
            visited[x][y] = true;
            DFSWithStack(grid, i: x+1, j: y)
            DFSWithStack(grid, i: x-1, j: y)
            DFSWithStack(grid, i: x, j: y+1)
            DFSWithStack(grid, i: x, j: y-1)
        }

    }
    

}

swift不熟，不夠優(yōu)雅代碼有冗余，輕噴！