1.最后一个单词的长度(很简单) 题目: 给定一个仅包含大小写字母和空格 ' ' 的字符串 s,返回其最后一个单词的长度. 如果字符串从左向右滚动显示,那么最后一个单词就是最后出现的单词. 如果不存在最后一个单词,请返回 0 . 说明:一个单词是指仅由字母组成.不包含任何空格的 最大子字符串. 示例: 输入: "Hello World" 输出: 5 代码: class Solution: def lengthOfLastWord(self, s: str) -> int: # 如…

贪心算法篇 # 题名 刷题 通过率 难度 44 通配符匹配   17.8% 困难 45 跳跃游戏 II   25.5% 困难 55 跳跃游戏   30.6% 中等 122 买卖股票的最佳时机 II C#LeetCode刷题之#122-买卖股票的最佳时机 II(Best Time to Buy and Sell Stock II) 48.8% 简单 134 加油站   40.0% 中等 135 分发糖果   33.0% 困难 316 去除重复字母   21.6% 困难 321 拼接最大数   20…

分治算法篇 # 题名 刷题 通过率 难度 4 两个排序数组的中位数 C#LeetCode刷题之#4-两个排序数组的中位数(Median of Two Sorted Arrays)-该题未达最优解 30.9% 困难 23 合并K个排序链表   39.4% 困难 53 最大子序和 C#LeetCode刷题之#53-最大子序和(Maximum Subarray)-该题包含分治讨论 38.4% 简单 169 求众数 C#LeetCode刷题之#169-求众数(Majority Element) 52.3…

回溯算法篇 # 题名 刷题 通过率 难度 10 正则表达式匹配   18.8% 困难 17 电话号码的字母组合   43.8% 中等 22 括号生成   64.9% 中等 37 解数独   45.8% 困难 39 组合总和   58.6% 中等 40 组合总和 II   49.6% 中等 44 通配符匹配   17.7% 困难 46 全排列   61.6% 中等 47 全排列 II   45.4% 中等 51 N皇后   55.2% 困难 52 N皇后 II   66.6% 困难 60 第k个排…

临近毕业了,对技术有种热爱的我也快步入码农行业了,以前虽然在学校的ACM学习过一些算法,什么大数的阶乘,dp,背包等,但是现在早就忘在脑袋后了,哈哈,原谅我是一枚菜鸡,为了锻炼编程能力还是去刷刷LeetCode吧       LeetCode收录了许多互联网公司的算法题目,被称为刷题神器.       主要的目的:       1.熟悉各互联网公司的算法题目,为找工作做准备,也为更好滴掌握编程能力.       2.复习以前学过的编程语言如java,c,c++,C#,LeetCode支持几乎所有…

运算符优先级,简单记就是:! > 算术运算符 > 关系运算符 > && > || > 赋值运算符 把数字取反,可以作为一种标记 pythonlast = {c: i for i, c in enumerate(S)}标记字符串S中每个字母的最后一个位置,存到字典last中 十分简洁的写法!!! 二分法规则: 如果是这么写while(left <= right) {},代表是左闭右闭区间 更新这么更新 { right = mid -1 left = mid…

异或.与的一点总结(这些位运算真的是骚操作2333) 两个相同的数字:a^a=0 取出一个数最右端为1的那一位:a &=-a 其中-a是在计算机中就是a的补码表示(这样所有的加法运算可以使用同一种电路完成),因为补码等于原码的反码+1,所以a&-a就是a最右边一位为1,其他位为0的数. 另外:~a = -a-1 ​ 已知负数的补码,求其原码:左右找1,此两1不变,中间取反. x&x-1 ==0 -判断 是否是2的n次方. -把一个整数减去1,再和原整数做与运算,会把该整数最右边一个…

所谓回溯算法,在笔者看来就是一种直接地思想----假设需要很多步操作才能求得最终的解,每一步操作又有很多种选择,那么我们就直接选择其中一种并依次深入下去.直到求得最终的结果,或是遇到明细的错误,回溯到上一步,换一种选择继续.就像把每种结果都遍历一遍,找到我们需要的结果. 回溯算法非常适合使用递归来求解,但与一般的递归又稍有不同.一个递归需要递归公式+递归终止条件,当然使用递归来实现的回溯算法也需要这些,只是就笔者的理解而言回溯算法还需要“回溯”这一部分.所谓回溯,就是在某一步中有多个选择的时候,…

Majority Element II Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. Note: The algorithm should run in linear time and in O(1) space. Example 1: Input: [3,2,3] Output: [3] Example 2: Input: [1,1,1,3,3,2,2,2] Ou…

Happy Number Write an algorithm to determine if a number n is "happy". A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the pr…

Maximum Gap Given an unsorted array, find the maximum difference between the successive elements in its sorted form. Return 0 if the array contains less than 2 elements. Example 1: Input: [3,6,9,1] Output: 3 Explanation: The sorted form of the array…

题目一: 给定一个文本文件 file.txt,请只打印这个文件中的第十行. 示例: 假设 file.txt 有如下内容: Line 1 Line 2 Line 3 Line 4 Line 5 Line 6 Line 7 Line 8 Line 9 Line 10 你的脚本应当显示第十行: Line 10 说明: 如果文件少于十行,你应当输出什么? 至少有三种不同的解法,请尝试尽可能多的方法来解题. # Read from the file file.txt and output the tent…

[题目描述] 给定一个数组 nums 和一个值 val,你需要原地移除所有数值等于 val 的元素,返回移除后数组的新长度. 不要使用额外的数组空间,你必须在原地修改输入数组并在使用 O(1) 额外空间的条件下完成. 元素的顺序可以改变.你不需要考虑数组中超出新长度后面的元素. 示例 1: 给定 nums = [3,2,2,3], val = 3, 函数应该返回新的长度 2, 并且 nums 中的前两个元素均为 2. 你不需要考虑数组中超出新长度后面的元素. 示例 2: 给定 nums = [0…

Range Sum Query - Mutable Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. The update(i, val) function modifies nums by updating the element at index i to val. Example: Given nums = [1, 3, 5] sumRa…

Additive Number Additive number is a string whose digits can form additive sequence. A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the prec…

Range Sum Query 2D - Immutable Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2). The above rectangle (with the red border) is defined by (row…

Longest Increasing Subsequence Given an unsorted array of integers, find the length of longest increasing subsequence. Example: Input: [10,9,2,5,3,7,101,18] Output: 4 Explanation: The longest increasing subsequence is [2,3,7,101], therefore the lengt…

Game of Life According to the Wikipedia's article: "The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970." Given a board with m by n cells, each cell has an initial…

Ugly Number II Write a program to find the n-th ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. Example: Input: n = 10 Output: 12 Explanation: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugl…

H-Index II Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index. According to the definition of h-index on Wikipedia: "A scientist has in…

Search a 2D Matrix II Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted in ascending from left to right. Integers in each column are sorted in ascendin…

Sliding Window Maximum Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position.…

Product of Array Except Self Given an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i]. Example: Input: [1,2,3,4] Output: [24,12,8,6] Constraint: It's…

Lowest Common Ancestor of a Binary Tree Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: "The lowest common ancestor is defined between two nodes p and q as th…

Kth Smallest Element in a BST Given a binary search tree, write a function kthSmallest to find the kth smallest element in it. Example 1: Input: root = [3,1,4,null,2], k = 1 3 / \ 1 4 \ 2 Output: 1 Example 2: Input: root = [5,3,6,2,4,null,null,1], k…

Summary Ranges Given a sorted integer array without duplicates, return the summary of its ranges. Example 1: Input: [0,1,2,4,5,7] Output: ["0->2","4->5","7"] Explanation: 0,1,2 form a continuous range; 4,5 form a contin…

Basic Calculator Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces ``. Example 1: Input: "1 + 1&…

Rectangle Area Find the total area covered by two rectilinear rectangles in a 2D plane. Each rectangle is defined by its bottom left corner and top right corner as shown in the figure. Example: Input: A = -3, B = 0, C = 3, D = 4, E = 0, F = -1, G = 9…

Count Complete Tree Nodes Given a complete binary tree, count the number of nodes. Note: Definition of a complete binary tree from Wikipedia: In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the…

Maximal Square Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area. Example: Input: 1 0 1 0 0 1 0 1 1 1 1 1 1 1 1 1 0 0 1 0 Output: 4 解 动态规划,设\(dp[i][j]\)表示下标为(i, j)的左上角区域的最大正方形面积,当\(\math…