［抄题］: Count the number of prime numbers less than a non-negative number, n. [暴力解法]: 时间分析: 空间分析: [优化后]: 时间分析: 空间分析: ［奇葩输出条件］: ［奇葩corner case］: ［思维问题］: ［一句话思路］: 质数的倍数是合数 ［输入量］:空: 正常情况:特大:特小:程序里处理到的特殊情况:异常情况(不合法不合理的输入): ［画图］: ［一刷］: ［二刷］: ［三刷］: ［四刷］: ［五刷…

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…

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. References: How Many Primes Are There? Sieve of Eratosthenes Credits:Special…

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 the number of prime numbers less than a non-negative number, n. 问题:找出所有小于 n 的素数. 题目很简洁,但是算法实现的优化层次有很多层.其中最主要思想的是采用 Sieve of Eratosthenes 算法来解答. 大思路为: 找出 n 范围内所有合数,并做标记. 未做标记的即为素数,统计未做标记的数个数即为原题目解. 如何找到 n 范围内所有合数? 将第一个素数 2 赋值给 i. 当 i 小于 n 时:(2)…

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(…

题目: 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. 分析: 统计所有小于非负整数 n 的质数的数量. 这里使用埃拉托斯特尼筛法.要得到自然数n以内的全部素数,必须把不大于√n的所有素数的倍数剔除,剩…

Description: Count the number of prime numbers less than a non-negative number, n click to show more hints. References: How Many Primes Are There? Sieve of Eratosthenes Credits:Special thanks to @mithmatt for adding this problem and creating all test…