Problem
Given an image represented by an N x N matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees. Can you do this in place?
Example
Given matrix =
[
[1,2,3],
[4,5,6],
[7,8,9]
],
Rotate the matrix in place. It becomes:
[
[7,4,1],
[8,5,2],
[9,6,3]
]
Example2
Given matrix =
[
[ 5, 1, 9,11],
[ 2, 4, 8,10],
[13, 3, 6, 7],
[15,14,12,16]
],
Rotate the matrix in place. It becomes:
[
[15,13, 2, 5],
[14, 3, 4, 1],
[12, 6, 8, 9],
[16, 7,10,11]
]
Solution
参照了书上的解法。
class Solution {
public:
void rotate(vector<vector<int>>& matrix) {
if(matrix.empty() || matrix.size() != matrix[0].size())
return;
int n = matrix.size();
for(int layer = 0;layer < n/2;++layer)
{
int first = layer;
int last = n -layer - 1;
for(int i = first;i<last;++i)
{
int offset = i - first;
int top = matrix[first][i]; //Store top
matrix[first][i] = matrix[last - offset][first];//Move left to top
matrix[last - offset][first] = matrix[last][last - offset];//Move bottom to left
matrix[last][last-offset] = matrix[i][last]; //Move right to bottom
matrix[i][last] = top; //Move top to right
}
}
}
};
