Rotate Image

youqika

于 2013-12-24 20:54:19 发布

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分类专栏： leetcode 文章标签： matrix rotate image

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本文介绍了一个用于二维矩阵(图像)的90度顺时针旋转算法，并提供了C++实现代码。该算法通过逐层旋转的方式实现了原地(in-place)操作，有效减少了额外的空间开销。

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You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

class Solution {
public:
void rotate(vector<vector<int> > &matrix) {                                 
        int s = matrix.size() - 1;                                              
                                                                                
        for (int n = s, c = 0; n > 0; n -= 2, ++c) {                            
            int tmp;                                                            
                                                                                
            for (int i = 0; i < n; ++i) {                                       
                // clockwise                                                    
                tmp = matrix[c][i + c];                                         
                matrix[c][i + c] = matrix[s - i - c][c];                        
                matrix[s - i - c][c] = matrix[s - c][s - i - c];                
                matrix[s - c][s - i - c] = matrix[i + c][s - c];                
                matrix[i + c][s - c] = tmp;                                     
                                                                                
                // anticlockwise                                                
                /*tmp = matrix[c][i + c];                                       
                matrix[c][i + c] = matrix[i + c][s - c];                        
                matrix[i + c][s - c] = matrix[s - c][s - i - c];                
                matrix[s - c][s - i - c] = matrix[s - i - c][c];                
                matrix[s - i - c][c] = tmp;*/               
                
                // print here to observ how it works                    
            }                                                                   
        }                                                                       
    }                    
};