1 Star 0 Fork 332

大宇 / leetcode

forked from doocs / leetcode 
加入 Gitee
与超过 1200万 开发者一起发现、参与优秀开源项目,私有仓库也完全免费 :)
免费加入
克隆/下载
README_EN.md 1.73 KB
一键复制 编辑 原始数据 按行查看 历史
ylb 提交于 2021-04-21 23:12 . feat: update leetcode problems description

204. Count Primes

中文文档

Description

Count the number of prime numbers less than a non-negative number, n.

 

Example 1:

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

Example 2:

Input: n = 0
Output: 0

Example 3:

Input: n = 1
Output: 0

 

Constraints:

  • 0 <= n <= 5 * 106

Solutions

Python3

class Solution:
    def countPrimes(self, n: int) -> int:
        if n < 2:
            return 0
        res = 0
        primes = [True for _ in range(n)]
        for i in range(2, n):
            if primes[i]:
                res += 1
                for j in range(i * i, n, i):
                    primes[j] = False
        return res

Java

class Solution {
    public int countPrimes(int n) {
        if (n < 2) return 0;
        boolean[] primes = new boolean[n];
        Arrays.fill(primes, true);
        int res = 0;
        for (int i = 2; i < n; ++i) {
            if (primes[i]) {
                ++res;
                if ((long) i * i < n) {
                    for (int j = i * i; j < n; j += i) {
                        primes[j] = false;
                    }
                }
            }
        }
        return res;
    }
}

...

马建仓 AI 助手
尝试更多
代码解读
代码找茬
代码优化
Java
1
https://gitee.com/fdayu/leetcode.git
git@gitee.com:fdayu/leetcode.git
fdayu
leetcode
leetcode
main

搜索帮助

344bd9b3 5694891 D2dac590 5694891