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
原文地址:https://www.cnblogs.com/yalphait/p/10355063.html
时间: 2024-09-30 07:25:32