count-primes

java

python

python3

mysql

mssql

oraclesql

csharp

javascript

typescript

bash

swift

kotlin

dart

golang

ruby

scala

rust

racket

erlang

elixir

pythondata

postgresql

cangjie

Algorithms

Given an integer <code>n</code>, return the number of prime numbers that are strictly less than <code>n</code>.

&nbsp;
Example 1:

<pre>
Input: n = 10
Output: 4
Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.
</pre>

Example 2:

<pre>
Input: n = 0
Output: 0
</pre>

Example 3:

<pre>
Input: n = 1
Output: 0
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>0 &lt;= n &lt;= 5 * 106</code></li>
</ul>

countPrimes

Count Primes

Ugly Number

ugly-number

丑数

Ugly Number II

ugly-number-ii

丑数 II

Perfect Squares

perfect-squares

完全平方数

Number of Common Factors

number-of-common-factors

公因子的数目

Prime Pairs With Target Sum

prime-pairs-with-target-sum

和等于目标值的质数对

Find the Count of Numbers Which Are Not Special

find-the-count-of-numbers-which-are-not-special

统计不是特殊数字的数字数量

Array

Math

Enumeration

Number Theory

给定整数 <code>n</code> ，返回 所有小于非负整数&nbsp;<code>n</code>&nbsp;的质数的数量 。

&nbsp;

示例 1：

<pre>
输入：n = 10
输出：4
解释：小于 10 的质数一共有 4 个, 它们是 2, 3, 5, 7 。
</pre>

示例 2：

<pre>
输入：n = 0
输出：0
</pre>

示例 3：

<pre>
输入：n = 1
输出：0
</pre>

&nbsp;

提示：

<ul>
	<li><code>0 &lt;= n &lt;= 5 * 106</code></li>
</ul>