Hihocoder 1165: Puzzle game

Time limit: 20000ms single point time limit: 1000ms memory limit: 256MB description

Fragrance today is in a good mood, and the flowers in the field of insects play a puzzle game.
This game is like this, for an array A, fragrance Select a number a from a, insects select a number b from a. A and B can be the same. Their score is the number of a*b factors.
The delicate fragrance and the worm of course want to get as high a score as possible, can you tell them which two number to choose?
Since the fragrance is a very casual person, the elements in array A are randomly chosen by her.

Input

A row of number N, which represents the number of integers in a.
The next line of N is the number of A1,A2,..., an, respectively, as an element of a.

n <= 100000, 1 <= ai <= 100000
Ensure that all AI are randomly generated.

Output

A row represents the maximum score.

How to think there is no algorithm, in fact, the right violent posture can also be a miracle.

At first, we only think of the number of factors b[i], and then skillfully use break;

This form: if (Ans>b[i]*b[j]) break a layer of loops, b arrays are sorted by the number of factors from large to small, so correct.

But each time we calculate the sum of the number of factors (a[i],a[j]), we have to enumerate through the past, TLE.

For example, this code:

#include <cstdio> #include <algorithm> #include <cmath> #include <string.h> #include <string >using namespace std; #define N 100001int p[n];int b[n],t;struct node{int x, y;}    A[n];void Prime () {for (Int. i=2;i<n;i++) if (!b[i]) for (int j=i+i;j<n;j+=i) b[j]=1; for (int i=2;i<n;i++) if (!b[i]) p[++t]=i;}   int work (int x,int y) {int sum=1;   int t=1;       while (1) {if (x==1&&y==1) return sum;       int v=1;               if (x%p[t]==0) {while (x%p[t]==0) {v++;           X/=P[T];               }} if (Y%p[t]==0) {while (y%p[t]==0) {v++;           Y/=P[T];       }} t++;   Sum*=v; }}int CMP (node A,node b) {return a.y>b.y;}    int main () {prime ();    Memset (b,0,sizeof (b));    int n;    scanf ("%d", &n);    for (int i=1;i<=n;i++) scanf ("%d", &a[i].x), A[i].y=work (a[i].x,1); for (int i=1;i<=n;i++) printf ("%d", a[i].y);    Sort (a+1,a+n+1,cmp);    int ans=0;    for (int i=1;i<=n;i++) for (int. j=i+1;j<=n;j++) {if (ans>a[i].y*a[j].y) break;    else Ans=work (a[i].x,a[j].x);    } printf ("%d\n", ans); return 0;}

So I see a template: Linear handsome, and each time we can find a number of the precursor prime factor

1#include <cstdio>2#include <algorithm>3#include <cmath>4#include <string.h>5#include <string>6 7 using namespacestd;8 9 #defineN 100001Ten  One intP[n]; A intb[n],t=0; -  - structnode the { -     intx, y; - }a[n]; - voidPrime () + { -     for(intI=2; i<n;i++) +    { A        if(!b[i]) p[++t]=b[i]=i; at         for(intj=1; j<=t&&p[j]<=b[i]&&p[j]<=n/i;++j) b[i*p[j]]=P[j]; -    } -b[1]=N; - } -  -  intWorkintXinty) in { -    intsum=1; to    intC=0; +     while(x>1|| Y>1) -    { the        if(B[x]<b[y]) c=B[x]; *        ElseC=B[y]; $        intv=1;Panax Notoginseng         for(; b[x]==c;x/=c) v++; -         for(; b[y]==c;y/=c) v++; thesum*=v; +    } A    returnsum; the } +InlineintCMP (node A,node b) - { $     returnA.y>b.y; $ } -  - intMain () the { - Prime ();Wuyi  the     intN; -scanf"%d",&n); Wu      for(intI=1; i<=n;i++) -scanf"%d", &a[i].x), A[i].y=work (a[i].x,1); About  $Sort (A +1, a+n+1, CMP); -     intans=a[1].y; -N=min (N, $); -  A      for(intI=1; i<=n;i++) +      for(intj=i+1; j<=n;j++){ the     if(ANS&GT;A[I].Y*A[J].Y) Break; -     Elseans=Max (Ans,work (a[i].x,a[j].x)); $     } the  theprintf"%d\n", ans); the     return 0; the}

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But you will find still very slow, super slow, 9000ms, and then look at a code, found!!

We enumerate the

for (int i=1;i<=n;i++) for    (int j=i+1;j<=n;j++)
Because n can be very large, about 100,000, but the back is mostly useless, so we just n<=1000, and so on is enough.

Violence is horrible.

Hihocoder 1165: Puzzle game