[Swift]LeetCode48. 旋转图像 | Rotate Image

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You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = 
[
  [1,2,3],
  [4,5,6],
  [7,8,9]
],
rotate the input matrix in-place such that it becomes:
[
  [7,4,1],
  [8,5,2],
  [9,6,3]
]

Example 2:

Given input matrix =
[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 
rotate the input matrix in-place such that it becomes:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]

---

给定一个 n × n 的二维矩阵表示一个图像。

将图像顺时针旋转 90 度。

说明：

你必须在原地旋转图像，这意味着你需要直接修改输入的二维矩阵。请不要使用另一个矩阵来旋转图像。

示例 1:

给定 matrix = 
[
  [1,2,3],
  [4,5,6],
  [7,8,9]
],
原地旋转输入矩阵，使其变为:
[
  [7,4,1],
  [8,5,2],
  [9,6,3]
]

示例 2:

给定 matrix =
[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 
原地旋转输入矩阵，使其变为:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]

---

8ms

class Solution 
{
    func rotate(_ matrix: inout [[Int]]) 
    {
        let temp = matrix;
        
        for i in 0..<matrix.count
        {
            for j in 0..<matrix[0].count
            {
                matrix[j][matrix[0].count - 1 - i] = temp[i][j];
            }
        }
    }
}

---

12ms

class Solution {
    func rotate(_ matrix: inout [[Int]]) {    
        matrix.reverse()
        
        for i in 1..<matrix.count {
            for j in 0..<i {
                (matrix[i][j], matrix[j][i]) = (matrix[j][i], matrix[i][j])
            }
        }
    }
}

---

16ms

class Solution {
    func rotate(_ matrix: inout [[Int]]) {
        let layers:Int = matrix.count / 2 - 1
        let n = matrix.count - 1
        var currentLayerWidth = n - 1    //layer的宽度,每一层转 currentLayerWidth次
        if layers < 0 {
            return 
        }
        for i in 0...layers {
            if currentLayerWidth < 0 {
                break
            }
            for j in 0...currentLayerWidth {  //每层旋转逻辑
                let x = i + j          //i 层级,x 移动点（相对整个矩阵）
                let firstPoint = matrix[i][x]
                matrix[i][x] = matrix[n - x][i]
                matrix[n - x][i] = matrix[n - i][n - x]
                matrix[n - i][n - x] = matrix[x][n - i]
                matrix[x][n - i] = firstPoint
            }
            //向内层靠近
            currentLayerWidth = currentLayerWidth - 2
        }
    }
}

---

16ms

class Solution {
    func rotate(_ matrix: inout [[Int]]) {
        let n = matrix.count
        
        for layer in 0..<n/2 {
            let start = layer
            let end = n - layer - 1
            
            for i in start..<end {
                let offset = i - start
                (matrix[start][i], matrix[i][end], matrix[end][end-offset], matrix[end-offset][start]) = ( matrix[end-offset][start], matrix[start][i], matrix[i][end], matrix[end][end-offset])
            }
        }
    }
}

---

20ms

class Solution {
    func rotate(_ matrix: inout [[Int]]) {
        let count = matrix[0].count
        for i in (0 ..< count)  {
            for t in (i ..< count) {
                let d = matrix[t][i]
                matrix[t][i] = matrix[i][t]
                matrix[i][t] = d 
            }
        }

        for i in (0 ..< count) {
            for t in (0 ..< (count + 1)/2 ) {
                let temp = matrix[i][t]
                matrix[i][t] = matrix[i][count - t - 1]
                matrix[i][count - t - 1] = temp
            }
        }
    }
}

---

28ms

class Solution {
    func rotate(_ matrix: inout [[Int]]) {
        let count = matrix.count
        for i in 0..<count {
            for j in i+1..<count {
                if i == j { return }
                // swap
                matrix[i][j] = matrix[i][j] ^ matrix[j][i]
                matrix[j][i] = matrix[i][j] ^ matrix[j][i]
                matrix[i][j] = matrix[i][j] ^ matrix[j][i]
            }
            matrix[i].reverse()
        }
    }
}

---

36ms

class Solution {
    func rotate(_ matrix: inout [[Int]]) {

        for item in 0...matrix.count-1 {
            for i in item...matrix.count-1 {
                let tmpItem = matrix[item][i]
                matrix[item][i] = matrix[i][item]
                matrix[i][item] = tmpItem
            }
        }
        for item in 0...matrix.count-1 {
            matrix[item].reverse()
        }
        
    }
}