LeetCode_Rotate Image

最新推荐文章于 2025-09-10 15:16:07 发布

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最新推荐文章于 2025-09-10 15:16:07 发布

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文章标签： c/c++

原文链接：http://www.cnblogs.com/graph/p/3229056.html

本文介绍了一种使用C++实现的二维矩阵（图像）顺时针旋转90度的方法。通过分层旋转的方式，在原地完成图像旋转，避免了额外的空间开销。详细展示了通过四向交换来旋转图像边缘的算法步骤。

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?

The rotation can be performed in layers, where you perform a cyclic swap on the edges on

each layer In the frst for loop, we rotate the frst layer (outermost edges) We rotate the
edges by doing a four-way swap frst on the corners, then on the element clockwise from the
edges, then on the element three steps away
Once the exterior elements are rotated, we then rotate the interior region’s edge

class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int n = matrix.size();
        if(n < 2) return ;
        for(int lay = 0 ; lay < n/2; lay ++){
              int first = lay ;
              int last = n - 1 - lay;
            for(int i = first; i< last; i++){
                int offset = i - first;
                //store the top
                int top = matrix[first][i] ;
                //left to top
                 matrix[first][i] = matrix[last - offset][first];
                 //bottom to left
                 matrix[last - offset][first] = matrix[last][last- offset];
                 //right to bottom
                 matrix[last][last - offset] = matrix[i][last];
                 //top to right
                 matrix[i][last] = top;        
            }
        }            
    }
};