leetcode - 48. Rotate Image - Medium descrition 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 direct…

# -*- coding: utf8 -*-'''__author__ = 'dabay.wang@gmail.com' 48: Rotate Imagehttps://leetcode.com/problems/rotate-image/ You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).Could you do this in-place? ===…

Question 48. Rotate Image Solution 把这个二维数组(矩阵)看成一个一个环,循环每个环,循环每条边,每个边上的点进行旋转 public void rotate(int[][] matrix) { int n = matrix.length; for (int i = 0; i < n / 2; i++) { change(matrix, i); } } private void change(int[][] matrix, int i) { int n = mat…

[11] Container With Most Water [Medium] O(n^2)的暴力解法直接TLE. 正确的解法是Two Pointers. O(n)的复杂度.保持两个指针i,j:分别指向长度数组的首尾.如果ai 小于aj,则移动i向后(i++).反之,移动j向前(j--).如果当前的area大于了所记录的area,替换之.这个想法的基础是,如果i的长度小于j,无论如何移动j,短板在i,不可能找到比当前记录的area更大的值了,只能通过移动i来找到新的可能的更大面积. class…

1. Two Sum Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution. Example: Given nums = [2, 7, 11, 15], target = 9, Because nums[0] + n…

一.题目说明 题目是48. Rotate Image,简而言之就是矩阵顺时针旋转90度.不允许使用额外的矩阵. 经过观察(写一个矩阵,多看几遍就知道了),旋转90度后: 第1行变为len-1列(最后一列),第i行变为 len-i-1列最终达到(i,j)-->(j,len-i-1) 知道规律后,做法就比较简单了,可以先上下行交换,再对角交换: (i,j)-->(len-i-1,j)-->(j,len-i-1) 也可以先对角交换,再左右列交换: (i,j)-->(j,i)-->(…

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…

189. Rotate Array Total Accepted: 55073 Total Submissions: 278176 Difficulty: Easy Rotate an array of n elements to the right by k steps. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. Note: Try to come up…

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…

189. 旋转数组 LeetCode189. Rotate Array 题目描述 给定一个数组,将数组中的元素向右移动 k 个位置,其中 k 是非负数. 示例 1: 输入: [1,2,3,4,5,6,7] 和 k = 3 输出: [5,6,7,1,2,3,4] 解释: 向右旋转 1 步: [7,1,2,3,4,5,6] 向右旋转 2 步: [6,7,1,2,3,4,5] 向右旋转 3 步: [5,6,7,1,2,3,4] 示例 2: 输入: [-1,-100,3,99] 和 k = 2 输出:…