Description:Count the number of prime numbers less than a non-negative number, n. Hint: Let's start with a isPrime function. To determine if a number is prime, we need to check if it is not divisible by any number less than n. The runtime complexity…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 素数筛法 参考资料 日期 [LeetCode] 题目地址:https://leetcode.com/problems/count-primes/ Total Accepted: 36655 Total Submissions: 172606 Difficulty: Easy 题目描述 Count the number of prime numbers…

Count Primes Count the number of prime numbers less than a non-negative number, *n*. Example: Input: 10 Output: 4 Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7. 解法1 埃氏筛法 class Solution { public: int countPrimes(int n) { if(…

[LeetCode]222. Count Complete Tree Nodes 解题报告(Python) 标签(空格分隔): LeetCode 作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.me/ 题目地址:https://leetcode.com/problems/count-complete-tree-nodes/description/ 题目描述: Given a complete binary tree, count the n…

#-*- coding: UTF-8 -*- #Hint1:#数字i,i的倍数一定不是质数,因此去掉i的倍数,例如5,5*1,5*2,5*3,5*4,5*5都不是质数,应该去掉#5*1,5*2,5*3,5*4 在数字1,2,3,4的时候都已经剔除过,因此数字5,应该从5*5开始#Hint2:#例:#2 × 6 = 12#3 × 4 = 12#4 × 3 = 12#6 × 2 = 12#显然4 × 3 = 12,和6 × 2 = 12不应该分析,因为在前两式中已经知道12不是质数,因此如果数字i是…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 记忆化搜索 动态规划 日期 题目地址:https://leetcode.com/problems/count-different-palindromic-subsequences/description/ 题目描述 Given a string S, find the number of different non-empty palindromic…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 方法一:暴力解法(TLE) 方法二:连续子串计算 日期 题目地址:https://leetcode.com/problems/baseball-game/description/ 题目描述 Give a string s, count the number of non-empty (contiguous) substrings that have…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 日期 题目地址:https://leetcode.com/problems/count-numbers-with-unique-digits/description/ 题目描述 Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x <…

The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ... 1 is read off as "one 1" or 11.11 is read off as "two 1s" or 21.21 is read off as "one 2, then one 1" or 1211. Given an…

题目描述: Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n. 解题分析: 题目要就就是找出 0≤ x < 10n中各位数字都不相同的数的个数.要接触这道题只需要理解: 1.设f(n)表示n为数字中各位都不相同的个数,则有countNumbersWithUniqueDigits(n)=f(1)+f(2)+……+f(n)=f(n)+countNumbersWithU…

题目: Given an integer array nums, return the number of range sums that lie in [lower, upper] inclusive. Range sum S(i, j) is defined as the sum of the elements in nums between indices i and  j (i ≤ j), inclusive. Note: A naive algorithm of O(n2) is tr…

Question: Given a complete binary tree, count the number of nodes. 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 last level are as far…

题目如下: Given an array of integers nums and an integer k. A subarray is called nice if there are k odd numbers on it. Return the number of nice sub-arrays. Example 1: Input: nums = [1,1,2,1,1], k = 3 Output: 2 Explanation: The only sub-arrays with 3 od…

题目如下: Given an integer n, your task is to count how many strings of length n can be formed under the following rules: Each character is a lower case vowel ('a', 'e', 'i', 'o', 'u') Each vowel 'a' may only be followed by an 'e'. Each vowel 'e' may onl…

问题描述: 统计所有小于非负整数 n 的质数的数量. 示例: 输入: 10 输出: 4 解释: 小于 10 的质数一共有 4 个, 它们是 2, 3, 5, 7 . 这是一道简单题,但是却并没有那么直接的简单. 枚举暴力法是肯定不行的,时间效率太低.于是介绍解决这个问题的一个著名算法--Eratosthenes筛选法. 来自 https://www.cnblogs.com/color-my-life/p/3265236.html 的解释,我觉得非常通俗易懂. 首先假设要检查的数是N好了,则事实上…

作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 组合数 日期 题目地址:https://leetcode-cn.com/problems/count-substrings-with-only-one-distinct-letter/ 题目描述 Given a string S, return the number of substrings that have only one distinct l…

题目如下: You are given a map of a server center, represented as a m * n integer matrix grid, where 1 means that on that cell there is a server and 0 means that it is no server. Two servers are said to communicate if they are on the same row or on the sa…

Given the root of a complete binary tree, return the number of the nodes in the tree. According to Wikipedia, every level, except possibly the last, is completely filled in a complete binary tree, and all nodes in the last level are as far left as po…

题目大意 https://leetcode.com/problems/count-primes/description/ 204. Count Primes Count the number of prime numbers less than a non-negative number, n. Example: Input: 10Output: 4Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.…

263. Ugly Number 注意:1.小于等于0都不属于丑数 2.while循环的判断不是num >= 0, 而是能被2 .3.5整除,即能被整除才去除这些数 class Solution { public: bool isUgly(int num) { ) return false; == ) num /= ; == ) num /= ; == ) num /= ; ? true : false; } }; 264. Ugly Number II 用一个数组去存第n个前面的所有整数,然后…

Queston 204. Count Primes Solution 题目大意:给一个数,求小于这个数的素数的个数 思路:初始化一个boolean数组,初始设置为true,先遍历将2的倍数设置为false,再遍历3并将3的倍数置为false... Java实现: 此法超时 public int countPrimes(int n) { // 2, 3, 5, 7 boolean[] candidate = new boolean[n]; Arrays.fill(candidate, Boolea…

[LeetCode]Minimum Depth of Binary Tree Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. 递归和非递归,此提比较简单.广度优先遍历即可.关键之处就在于如何保持访问深度. 下面是4种代码: im…

27. Remove Element[leetcode] Given an array and a value, remove all instances of that value in place and return the new length. Do not allocate extra space for another array, you must do this in place with constant memory. The order of elements can b…

题目如下: 解题思路:本题是[leetcode]473. Matchsticks to Square的姊妹篇,唯一的区别是[leetcode]473. Matchsticks to Square指定了分成四个子数组,而本题分成的份数不定,作为参数输入.另外,本题的测试用例好像复杂一点,因此我过滤掉了nums中值等于avg的元素,不参与后面的DFS计算,提高效率. 代码如下: class Solution(object): def canPartitionKSubsets(self, nums,…

题目如下: 解题思路:和[leetcode]84. Largest Rectangle in Histogram的核心是一样的,都是要找出当前元素之前第一个大于自己的元素. 代码如下: class StockSpanner(object): def __init__(self): self.cl = [] self.vl = [] def next(self, price): """ :type price: int :rtype: int """…

题目如下: On an NxN chessboard, a knight starts at the r-th row and c-th column and attempts to make exactly K moves. The rows and columns are 0 indexed, so the top-left square is (0, 0), and the bottom-right square is (N-1, N-1). A chess knight has 8 po…

目录 二分查找 排序的写法 BFS的写法 DFS的写法 回溯法 树 递归 迭代 前序遍历 中序遍历 后序遍历 构建完全二叉树 并查集 前缀树 图遍历 Dijkstra算法 Floyd-Warshall算法 Bellman-Ford算法 最小生成树 Kruskal算法 Prim算法 拓扑排序 双指针 动态规划 状态搜索 贪心 本文的目的是收集一些典型的题目,记住其写法,理解其思想,即可做到一通百通.欢迎大家提出宝贵意见! 博主有算法题解的微信公众号啦,欢迎关注「负雪明烛」,持续更新算法题的解题思路…

[LeetCode]Island Perimeter 解题报告 [LeetCode] https://leetcode.com/problems/island-perimeter/ Total Accepted: 16143 Total Submissions: 28552 Difficulty: Easy Question You are given a map in form of a two-dimensional integer grid where 1 represents land…

[LeetCode]697. Degree of an Array 解题报告 标签(空格分隔): LeetCode 题目地址:https://leetcode.com/problems/degree-of-an-array/description/ 题目描述: Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of…

[LeetCode]657. Judge Route Circle 标签(空格分隔): LeetCode 题目地址:https://leetcode.com/problems/judge-route-circle/description/ 题目描述: Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot makes a circle, which mea…