Max Factor
Time Limit:1000MS Memory Limit:32768KB 64bit IO Format:%I64d & %I64u
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
4 36 38 40 42
Sample Output
38 比较水xjb做新风格不错 以后就这样写了
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <vector>
#include <iomanip>
#include <math.h>
#include <map>
using namespace std;
#define FIN freopen("input.txt","r",stdin);
#define INF 0x3f3f3f3f
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
typedef long long LL;
const int MAXN=20005;
int p[MAXN];
int main()
{
//FIN
p[1]=1;
int cou=0;
for(int i=2; i<=20005; i++)
{
if(p[i]==0)
{
cou++;
for(int j=i; j<=20005; j=j+i)
{
p[j]=cou;
}
}
}
int n;
while(~scanf("%d",&n))
{
int ans=0,pos;
int x;
for(int i=1;i<=n;i++){
scanf("%d",&x);
if(p[x]>ans) {ans=p[x];pos=x;}
}
printf("%d\n",pos);
}
}