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  • [Leetcode] Rotate Image

    Rotate Image 题解

    题目来源:https://leetcode.com/problems/rotate-image/description/


    Description

    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

    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]
    ]
    

    Solution

    class Solution {
    public:
        void rotate(vector<vector<int> >& matrix) {
            int n = matrix.size();
            reverse(matrix.begin(), matrix.end());
            int i, j;
            for (i = 0; i < n; i++) {
                for (j = i; j < n; j++)
                    swap(matrix[i][j], matrix[j][i]);
            }
        }
    };
    

    解题描述

    这道题题意是,给出一个正方形的矩阵代表一副图像,求将图像顺时针旋转之后的矩阵,并且要求原地旋转,不能申请新的矩阵。上面用到的解法是,先将矩阵进行上下翻转,然后再进行对角线上的翻转即可。

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  • 原文地址:https://www.cnblogs.com/yanhewu/p/8416228.html
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