标签：swa level represent image style color http auto begin
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?
先贴上自己丑陋的代码：主要思路是把最外面一圈旋转好，然后由外向内不断转一圈。
class Solution { public: void rotate(vector<vector<int>>& matrix,int n,int level){ for(int i=0;i<n-1;i++){ int temp=matrix[level][i+level]; matrix[level][i+level]=matrix[n-1-i+level][level]; matrix[n-1-i+level][level]=matrix[n-1+level][n-1-i+level]; matrix[n-1+level][n-1-i+level]=matrix[i+level][n-1+level]; matrix[i+level][n-1+level]=temp; } } void rotate(vector<vector<int>>& matrix) { int n=matrix.size(); for(int i=n;i>=2;i-=2) rotate(matrix,i,(n-i)/2); } };
然后学习下正确的翻转姿势：https://discuss.leetcode.com/topic/6796/a-common-method-to-rotate-the-image
class Solution { public: /* * clockwise rotate * first reverse up to down, then swap the symmetry * 1 2 3 7 8 9 7 4 1 * 4 5 6 => 4 5 6 => 8 5 2 * 7 8 9 1 2 3 9 6 3 */ void rotate(vector<vector<int> > &matrix) { reverse(matrix.begin(), matrix.end()); for (int i = 0; i < matrix.size(); ++i) { for (int j = 0; j < i; ++j) swap(matrix[i][j], matrix[j][i]); } } /* * anticlockwise rotate * first reverse left to right, then swap the symmetry * 1 2 3 3 2 1 3 6 9 * 4 5 6 => 6 5 4 => 2 5 8 * 7 8 9 9 8 7 1 4 7 */ void anti_rotate(vector<vector<int> > &matrix) { for (auto vi : matrix) reverse(vi.begin(), vi.end()); for (int i = 0; i < matrix.size(); ++i) { for (int j = 0; j < i; ++j) swap(matrix[i][j], matrix[j][i]); } } };
标签：swa level represent image style color http auto begin
原文地址：http://www.cnblogs.com/tsunami-lj/p/6659486.html
