19.2.7 [LeetCode 48] Rotate Image

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

19.2.7 [LeetCode 48] Rotate Image的相关文章

LeetCode 48. Rotate Image(旋转图像)

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? 题目标签:Array 这道题目给了我们一个n * n的矩阵,让我们旋转图片.题目要求in-place,所以就不能用额外的空间了.一开始自己写了一个很原始的方法,结果虽然通过,但是速度太慢.只好去看看别人的方法,看完觉得,自己

19.2.9 [LeetCode 61] Rotate List

Given a linked list, rotate the list to the right by k places, where k is non-negative. Example 1: Input: 1->2->3->4->5->NULL, k = 2 Output: 4->5->1->2->3->NULL Explanation: rotate 1 steps to the right: 5->1->2->3-&g

Leetcode 48 Rotate Image

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? 思路:把矩阵看成是由多个正方形一层一层包围起来的.转动的时候就是转动正方形的边,只要把边上的每个数依次替换就好,四个方向也就是进行四次替换,依次对每一层进行替换. 总层数 = matrix.length/2,第i层从第mat

LeetCode 48. Rotate Image My Submissions Question (矩阵旋转)

题目大意:给一个矩阵,将其按顺时针旋转90°. 题目分析:通法是先将矩阵转置,然后再反转每一行,或者是先反转每一列,然后再将其转置.I just want to say"It's amazing!".(forgivig my poor English!) 代码如下(代码怎么写已经不重要了!): class Solution { public: void rotate(vector<vector<int>>& matrix) { int r=matrix.

leetCode 48.Rotate Image (旋转图像) 解题思路和方法

Rotate Image 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? 思路:其实就是旋转数组,没有什么难度,代码如下: public class Solution { public void rotate(int[][] matrix) { int[][] a =

LeetCode 48. Rotate Image (C++)

题目: 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

[LeetCode] 61. Rotate List 旋转链表

Given a linked list, rotate the list to the right by k places, where k is non-negative. Example 1: Input: 1->2->3->4->5->NULL, k = 2 Output: 4->5->1->2->3->NULL Explanation: rotate 1 steps to the right: 5->1->2->3-&g

LeetCode --- 61. Rotate List

题目链接:Rotate List Given a list, rotate the list to the right by k places, where k is non-negative. For example: Given 1->2->3->4->5->NULL and k = 2, return 4->5->1->2->3->NULL. 这道题的要求是向右旋转链表k步. 其实就是把链表后面l-k个节点放到前面,可以采用快慢指针处理.不

【Leetcode】Rotate Image

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? 思路:第一种思路是一层一层的进行旋转,比较直观:第二种思路则比较取巧,首先沿着副对角线翻转一次,然后沿着水平中线翻转一次. 代码一: class Solution { public: void rotate(vector<