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] ] ■ ■ ■ □ ■ ■ ■ □ ■ ■ ■ □ ■ ■ ■ ■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);
- }