Rotate Image

Desicription

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:

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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:

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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]
]

Solution

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class Solution {
public:
void rotate(vector<vector<int>>& matrix) {
int len = matrix.size();
vector<vector<int>> res(len, vector<int>(len));
for(int i = 0, j = len - 1; i < len; i++, j--){
for(int k = 0; k < len; k++)
res[k][j] = matrix[i][k];
}
matrix = res;
}
};