2070. Interesting Numbers Time limit: 2.0 secondMemory limit: 64 MB Nikolay and Asya investigate integers together in their spare time. Nikolay thinks an integer is interesting if it is a prime number. However, Asya thinks an integer is interesting i…

题意:在[L, R]之间求:x是个素数,因子个数是素数,同时满足两个条件,或者同时不满足两个条件的数的个数. 析:很明显所有的素数,因数都是2,是素数,所以我们只要算不是素数但因子是素数的数目就好,然后用总数减掉就好.打个表,找找规律,你会发现, 这些数除外的数都是素数的素数次方,然后就简单了. 代码如下: #pragma comment(linker, "/STACK:1024000000,1024000000") #include <cstdio> #include &…

素数必然符合题意. 对于合数,如若它是某个素数x的k次方(k为某个素数y减去1),一定不符合题意.只需找出这些数. 由约数个数定理,其他合数一定符合题意. 就从小到大枚举素数,然后把它的素数-1次方都排除即可. #include<cstdio> #include<cmath> using namespace std; #define MAXP 1000100 #define EPS 0.00000001 typedef long long ll; ll L,R; bool isNo…

题目传送门 /* 题意:n位数字,任意连续的三位数字组成的数字是素数,这样的n位数有多少个 最优子结构:考虑3位数的数字,可以枚举出来,第4位是和第3位,第2位组成的数字判断是否是素数 所以,dp[i][j][k] 表示i位数字,最高位数字j,第二高位数字k 状态转移方程:dp[i][j][k] += dp[i-1][k][l] 注意:最高位从1开始枚举:) 详细解释:http://blog.csdn.net/zhangyanxing666/article/details/9628563 */…

题目传送门 题意:n位数,k进制,求个数分析:dp[i][j] 表示i位数,当前数字为j的个数:若j==0,不加dp[i-1][0]; 代码1: #include <cstdio> #include <iostream> #include <algorithm> #include <cstring> using namespace std; const int MAXN = 22; const int INF = 0x3f3f3f3f; long long…

目录 1 问题描述 2 解决方案   1 问题描述 Problem Description We call a number interesting, if and only if: 1. Its digits consists of only 0, 1, 2 and 3, and all these digits occurred at least once. 2. Inside this number, all 0s occur before any 1s, and all 2s occur…

1 问题描述 Problem Description We call a number interesting, if and only if: 1. Its digits consists of only 0, 1, 2 and 3, and all these digits occurred at least once. 2. Inside this number, all 0s occur before any 1s, and all 2s occur before any 3s. The…

http://acm.timus.ru/problem.aspx?space=1&num=2070 题意:A认为如果某个数为质数的话,该数字是有趣的.B认为如果某个数它分解得到的因子数目是素数的话,那么该数字是有趣的. 现在问[L,R]里面有多少个数是同时满足这两个条件或者同时不满足这两个条件的数. 简化题意就是,用[L,R]里面的总数 - 是一个合数并且其因子数是素数的数目. 一开始想,如果是平方的话,那么因子数必定是一个奇数,但是奇数里面的素数要怎么找就不知道了.想到后面离正解越走越远. 正…

2031. Overturned Numbers Time limit: 1.0 second Memory limit: 64 MB Little Pierre was surfing the Internet and came across an interesting puzzle: What is the number under the car? It took some time before Pierre solved the puzzle, but eventually he u…

1150. Page Numbers Time limit: 1.0 secondMemory limit: 64 MB John Smith has decided to number the pages in his notebook from 1 to N. Please, figure out the number of zeros, ones, twos, …, nines he might need. Input One number N (1 ≤ N < 109). Output…