# C#LeetCode刷题之#48-旋转图像（Rotate Image）

[
[1,2,3],
[4,5,6],
[7,8,9]
],

[
[7,4,1],
[8,5,2],
[9,6,3]
]

[
[ 5, 1, 9,11],
[ 2, 4, 8,10],
[13, 3, 6, 7],
[15,14,12,16]
],

[
[15,13, 2, 5],
[14, 3, 4, 1],
[12, 6, 8, 9],
[16, 7,10,11]
]

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.

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]
]

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]
]

```public class Program {

public static void Main(string[] args) {
var matrix = new int[,] {
{ 1, 2, 3 },
{ 4, 5, 6 },
{ 7, 8, 9 }
};

Rotate(matrix);
ShowArray(matrix);

matrix = new int[,] {
{ 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 11, 12 },
{ 13, 14, 15, 16 }
};

Rotate2(matrix);
ShowArray(matrix);

}

private static void ShowArray(int[,] matrix) {
var length = matrix.GetLength(0);
for(var i = 0; i < length; i++) {
for(var j = 0; j < length; j++) {
Console.Write(\$"{ matrix[i, j]} ");
}
Console.WriteLine();
}
Console.WriteLine();
}

public static void Rotate(int[,] matrix) {
var length = matrix.GetLength(0);
for(var i = 0; i < length; i++) {
for(var j = i; j < length; j++) {
var swap = matrix[i, j];
matrix[i, j] = matrix[j, i];
matrix[j, i] = swap;
}
}
for(var i = 0; i < length; i++) {
for(var j = 0; j < length / 2; j++) {
var swap = matrix[i, j];
matrix[i, j] = matrix[i, length - j - 1];
matrix[i, length - j - 1] = swap;
}
}
}

public static void Rotate2(int[,] matrix) {
var length = matrix.GetLength(0);
for(var i = 0; i < length / 2; i++) {
for(var j = i + 1; j < length - i; j++) {
var swap = matrix[i, j];
matrix[i, j] = matrix[length - 1 - j, i];
matrix[length - 1 - j, i] = matrix[length - 1 - i, length - 1 - j];
matrix[length - 1 - i, length - 1 - j] = matrix[j, length - 1 - i];
matrix[j, length - 1 - i] = swap;
}
}
}

}```

```7 4 1
8 5 2
9 6 3

13 9 5 1
14 10 6 2
15 11 7 3
16 12 8 4```

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