Manthan, Codefest 16 B 数学

B. A Trivial Problem
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Mr. Santa asks all the great programmers of the world to solve a trivial problem. He gives them an integer m and asks for the number of positive integers n, such that the factorial of n ends with exactly m zeroes. Are you among those great programmers who can solve this problem?

Input

The only line of input contains an integer m (1 ≤ m ≤ 100 000) — the required number of trailing zeroes in factorial.

Output

First print k — the number of values of n such that the factorial of n ends with m zeroes. Then print these k integers in increasing order.

Examples
Input
1
Output
5
5 6 7 8 9
Input
5
Output
0
Note

The factorial of n is equal to the product of all integers from 1 to n inclusive, that is n! = 1·2·3·...·n.

In the first sample, 5! = 120, 6! = 720, 7! = 5040, 8! = 40320 and 9! = 362880.

题意:统计哪些数阶乘的末尾有m位‘0’    输出个数 并按照升序输出这些数

题解:数学知识  涨姿势

        我们知道阶乘下 产生‘0’位只能是 2*5=10产生‘0’位

        那么‘0’位的个数取决于‘2’和‘5’的个数

        相比之下‘5’的个数更少  所以末尾‘0’的个数取决于阶乘中‘5’的数

        所以可以预处理出所有数含有因数‘5’的个数 也就代码中fun的作用

        vector存储为一个数x 对应的x!中5的个数也就是结果。

       

 1 #include<bits/stdc++.h>
 2 #define ll __int64
 3 #define mod 1e9+7
 4 #define PI acos(-1.0)
 5 #define bug(x) printf("%%%%%%%%%%%%%",x);
 6 #define inf 1e8
 7 using namespace std;
 8 #define ll __int64
 9 int fun( int x)
10 {
11     int flag=0;
12     if(x%5==0)
13     {
14         while(x%5==0)
15         {
16             x/=5;
17             flag++;
18         }
19     }
20     return flag;
21 }
22 vector<int>ve[100005];
23 int m;
24 int main()
25 {
26     scanf("%d",&m);
27     int gg=0;
28     for(int i=1;i<=500000;i++)
29     {
30         gg+=fun(i);
31         if(gg==m)
32         ve[gg].push_back(i);
33     }
34     printf("%d
",ve[m].size());
35     if(ve[m].size())
36     cout<<ve[m][0];
37     for(int i=1;i<ve[m].size();i++)
38         cout<<" "<<ve[m][i];
39     cout<<endl;
40     return 0;
41 }
原文地址:https://www.cnblogs.com/hsd-/p/5675031.html