POJ3048 Max Factor

 1 //It is made by ljh2000
 2 #include <iostream>
 3 #include <cstdlib>
 4 #include <cstring>
 5 #include <cstdio>
 6 #include <cmath>
 7 #include <algorithm>
 8 #include <ctime>
 9 #include <vector>
10 #include <queue>
11 #include <map>
12 #include <set>
13 #include <string>
14 #include <stack>
15 using namespace std;
16 typedef long long LL;
17 const int MAXN = 50011;
18 const int MAXM = 200011; 
19 int n,N,a[MAXN],maxl[MAXN];
20 int cnt,prime[MAXM],ans;
21 bool vis[MAXM];
22 
23 inline int getint(){
24     int w=0,q=0; char c=getchar(); while((c<‘0‘||c>‘9‘) && c!=‘-‘) c=getchar();
25     if(c==‘-‘) q=1,c=getchar(); while (c>=‘0‘&&c<=‘9‘) w=w*10+c-‘0‘,c=getchar(); return q?-w:w;
26 }
27 
28 inline void work(){
29     n=getint(); for(int i=1;i<=n;i++) a[i]=getint(),N=max(a[i],N); ans=1; int x;
30     for(int i=2;i<=N;i++) { if(!vis[i]) prime[++cnt]=i; for(int j=1;j<=cnt && i*prime[j]<=N;j++) { vis[i*prime[j]]=1; if(i%prime[j]==0) break;} }
31     for(int i=1;i<=n;i++) {
32     x=a[i];
33     for(int j=1;j<=cnt;j++) {
34         if(x%prime[j]!=0) continue;
35         maxl[i]=prime[j]; while(x%prime[j]==0) x/=prime[j];
36         if(x==1) break;
37     }
38     }
39     for(int i=2;i<=n;i++) if(maxl[i]>maxl[ans]) ans=i;
40     printf("%d",a[ans]);
41 } 
42 
43 int main()
44 {
45     work();
46     return 0;
47 }