# Rotate Image Problem

## Description

LeetCode Problem 48.

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

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:

``````1
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Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]
``````

Example 2:

``````1
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Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
``````

Example 3:

``````1
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Input: matrix = [[1]]
Output: [[1]]
``````

Example 4:

``````1
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Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]
``````

Constraints:

• matrix.length == n
• matrix[i].length == n
• 1 <= n <= 20
• -1000 <= matrix[i][j] <= 1000

## Sample C++ Code

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class Solution {
public:
void rotate(vector<vector<int>>& matrix) {
int n = matrix.size();

int b = 0, e = n;
int tmp;
while (b <= e) {
for (int i = b; i < e-1; i ++) {
tmp = matrix[b][i];
matrix[b][i] = matrix[e-i+b-1][b];
matrix[e-i+b-1][b] = matrix[e-1][e-i+b-1];
matrix[e-1][e-i+b-1] = matrix[i][e-1];
matrix[i][e-1] = tmp;
}
b ++, e --;
}
}
};
``````