dp(i, j, k)表示共i位, 最高位是j, 数字k出现次数. 预处理出来. 差分答案, 对于0~x的答案, 从低位到高位进行讨论 ------------------------------------------------------------------------------ #include<bits/stdc++.h> using namespace std; typedef long long ll; const int maxn = 16; const in
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
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