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]
]
题意
在没有额外空间的前提下90度顺时针旋转n*n矩阵
题解
日常暴力↓
1 class Solution { 2 public: 3 void rotate(vector<vector<int>>& matrix) { 4 int n = matrix.size(), layer = n / 2; 5 for (int i = 0; i < layer; i++) { 6 for (int j = i; j < n - 1 - i; j++) { 7 int now = matrix[i][j]; 8 matrix[i][j] = matrix[n - 1 - j][i]; 9 matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j]; 10 matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i]; 11 matrix[j][n - 1 - i] = now; 12 } 13 } 14 } 15 };
但是问题是也找不到更快的解法,逐渐怀疑是不是今天系统的问题....beat 2%也太夸张了,大家都是咋做的啊