螺旋矩阵

59. 螺旋矩阵 II

给定一个正整数 n，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的正方形矩阵。
示例:
输入: 3
输出:
[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]

func generateMatrix(_ n: Int) -> [[Int]] {
        var result = [[Int]](repeating: [Int](repeating: 0, count: n), count: n)
        var top = 0, bottom = n - 1, left = 0, right = n - 1
        var num = 1
        while top <= bottom && left <= right {
            for i in stride(from: left, through: right, by: 1) {
                result[top][i] = num
                num += 1
            }
            top += 1
            
            for i in stride(from: top, through: bottom, by: 1) {
                result[i][right] = num
                num += 1
            }
            right -= 1
            
            if top <= bottom {
                for i in stride(from: right, through: left, by: -1) {
                    result[bottom][i] = num
                    num += 1
                }
            }
            bottom -= 1
            
            if left <= right {
                for i in stride(from: bottom, through: top, by: -1) {
                    result[i][left] = num
                    num += 1
                }
            }
            left += 1
        }
        
        return result
    }

    func generateMatrix_1(_ n: Int) -> [[Int]] {
        var result = [[Int]](repeating: [Int](repeating: 0, count: n), count: n)
        let directions = [[0, 1], [1, 0], [0, -1], [-1, 0]]
        var row = 0, column = 0, current = 0
        for i in 0..<n*n {
            result[row][column] = i + 1
            let nextRow = row + directions[current][0]
            let nextColumn = column + directions[current][1]
            if nextRow < 0 || nextRow >= n || nextColumn < 0 || nextColumn >= n || result[nextRow][nextColumn] != 0 {
                current = (current + 1) % 4
                row = row + directions[current][0]
                column = column + directions[current][1]
            } else {
                row = nextRow
                column = nextColumn
            }
        }
        return result
    }

54. 螺旋矩阵

给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。
示例 1:
输入:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
输出: [1,2,3,6,9,8,7,4,5]
示例 2:
输入:
[
[1, 2, 3, 4],
[5, 6, 7, 8],
[9,10,11,12]
]
输出: [1,2,3,4,8,12,11,10,9,5,6,7]

 func spiralMatrix(_ matrix:[[Int]]) -> [Int] {
           if matrix.count == 0 {return []}
             let row = matrix.count - 1
             let column = matrix[0].count - 1
             var result = [Int]()
             var left = 0, right = column
             var top = 0, bottom = row
             
             while left <= right && top <= bottom {
                 for i in stride(from: left, through: right, by: 1) {
                     result.append(matrix[top][i])
                 }
               top += 1
                // 上下符合的左右也必须符合答案才正确
               if left <= right {
                   for i in stride(from: top, through: bottom, by: 1) {
                        result.append(matrix[i][right])
                    }
               }
                
               right -= 1
               if top <= bottom {
                   for i in stride(from: right, through: left, by: -1) {
                        result.append(matrix[bottom][i])
                    }
               }
                
              bottom -= 1
               if left <= right {
                   for i in stride(from: bottom, through: top, by: -1) {
                        result.append(matrix[i][left])
                   }
               }
                
                 left += 1
             }
             return result
             
         }