# 旋转图像
给定一个 n × n 的二维矩阵 matrix 表示一个图像。请你将图像顺时针旋转 90 度。
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：
输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
输出：[[7,4,1],[8,5,2],[9,6,3]]
示例 2：
输入：matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
输出：[[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
示例 3：
输入：matrix = [[1]]
输出：[[1]]
示例 4：
输入：matrix = [[1,2],[3,4]]
输出：[[3,1],[4,2]]
提示：
matrix.length == nmatrix[i].length == n1 <= n <= 20-1000 <= matrix[i][j] <= 1000
以下错误的选项是？
## aop
### before
```c
```
### after
```c
```
## 答案
```c
class Solution
{
public:
void rotate(vector> &matrix)
{
int n = matrix.size();
int temp = 0;
for (int i = 0; i < n; ++i)
{
for (int j = i; j < n; ++j)
{
temp = matrix[i][j];
matrix[i][j] = matrix[n - j - 1][i];
matrix[j][i] = temp;
}
}
for (int i = 0; i < n; ++i)
{
reverse(matrix[i].begin(), matrix[i].end());
}
}
};
```
## 选项
### A
```c
class Solution
{
public:
void rotate(vector> &matrix)
{
int temp = 0;
int n = matrix.size();
for (int i = 0; i < n / 2; i++)
{
for (int j = i; j < n - i - 1; j++)
{
temp = matrix[i][j];
matrix[i][j] = matrix[n - j - 1][i];
matrix[n - j - 1][i] = matrix[n - i - 1][n - j - 1];
matrix[n - i - 1][n - j - 1] = matrix[j][n - i - 1];
matrix[j][n - i - 1] = temp;
}
}
}
};
```
### B
```c
class Solution
{
public:
void rotate(vector> &matrix)
{
int n = matrix.size();
int tmp = 0;
for (int i = 0; i < n; i++)
for (int j = i; j < n; j++)
{
tmp = matrix[j][i];
matrix[j][i] = matrix[i][j];
matrix[i][j] = tmp;
}
for (int i = 0; i < n; i++)
for (int j = 0; j < n / 2; j++)
{
tmp = matrix[i][j];
matrix[i][j] = matrix[i][n - j - 1];
matrix[i][n - j - 1] = tmp;
}
}
};
```
### C
```c
class Solution
{
public:
void rotate(vector> &matrix)
{
int n = matrix.size();
vector> matrix_temp = matrix;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
matrix_temp[j][n - i - 1] = matrix[i][j];
}
}
matrix = matrix_temp;
}
};
```