lc0048

48. Rotate Image

Medium

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:

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:

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]
]

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		按由外到内逐层旋转，虽然矩阵每层规模size，但是实际一层的每一边只需要 
	

	

		旋转size-1个元素， 
	

	

		
		
void rotate_one_layer(int** m, int o, int size)
{
    int p,tmp;
    for(p=0; p<size-1; ++p){
        tmp = m[o][o+p];
        m[o][o+p] = m[o+size-1-p][o];
        m[o+size-1-p][o] = m[o+size-1][o+size-1-p];
        m[o+size-1][o+size-1-p] = m[o+p][o+size-1];
        m[o+p][o+size-1] = tmp;
    }
}
void rotate(int** matrix, int matrixRowSize, int *matrixColSizes) {
    int layer;
    for(layer=0; layer<matrixRowSize/2; ++layer)
        rotate_one_layer(matrix, layer, matrixRowSize-layer*2);
}