杭电2710-Max Factor

Max Factor

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 2793    Accepted Submission(s): 873

Problem Description

To improve the organization of his farm, Farmer John labels each of his N (1 <= N <= 5,000) cows with a distinct serial number in the range 1..20,000. Unfortunately, he is unaware that the cows interpret some serial numbers as better than others. In particular, a cow whose serial number has the highest prime factor enjoys the highest social standing among all the other cows.

(Recall that a prime number is just a number that has no divisors except for 1 and itself. The number 7 is prime while the number 6, being divisible by 2 and 3, is not).

Given a set of N (1 <= N <= 5,000) serial numbers in the range 1..20,000, determine the one that has the largest prime factor.

 

Input

* Line 1: A single integer, N

* Lines 2..N+1: The serial numbers to be tested, one per line

 

Output

* Line 1: The integer with the largest prime factor. If there are more than one, output the one that appears earliest in the input file.

 

Sample Input

436384042

 

Sample Output

38
题目的意思是求给出的几个数值中的最大且为素数的除数（即求本身范围内的最大素数比其他数的本身最大素数还要大的数）AC代码：#include<iostream>/*题目的意思是求给出的几个数值中的最大且为素数的除数*/  const int MAX=20005;int s[MAX];using namespace std;int main(){int n,m,maxn,i,j,p;memset(s,0,sizeof(s));s[1]=1;for(i=2;i<MAX;i++)//筛选所有范围内的素数 {if(s[i]==0)for(j=i;j<MAX;j+=i){s[j]=i;}}while(cin>>n){maxn=-1;while(n--){cin>>m;if(s[m]>maxn){maxn=s[m];p=m;}}cout<<p<<endl;}return 0;}