2015
05-24

# Maximum Number Of Divisors

You are given an integer P, please find an integer K that has the maximum number of divisors under the condition that K <= P.
Note that if multiple integers have the same number of divisors, please choose the smallest one.

The input consists of multiple test cases.
For each case, the input contains a single line with one integer P(1 <= P <= 1080)

The input consists of multiple test cases.
For each case, the input contains a single line with one integer P(1 <= P <= 1080)

100
10
1000000000000000

60 12
6 4
866421317361600 26880

import java.io.BufferedInputStream;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Scanner;

class Node
{
private static final int MAXP = 60;

public BigInteger K;
public long F;
public int N;
public int[] A;

public Node()
{
K = BigInteger.ZERO;
A = new int[MAXP];
}
}

public class Main
{
private static final int MAXIP = 250;
private static final int MAXP = 60;

private static BigInteger[] prime;

private static void init()
{
boolean[] isPrime = new boolean[MAXIP];
for(int i=0;i<MAXIP;++i)
{
isPrime[i] = true;
}
isPrime[0] = isPrime[1] = false;
for(int i=4;i<MAXIP;i+=2)
{
isPrime[i] = false;
}
for(int i=3;i<MAXIP;i+=2)
{
for(int j=3;i*j<MAXIP;j+=2)
{
isPrime[i*j] = false;
}
}
prime = new BigInteger[MAXP];
for(int i=0, j=0;i<MAXIP;++i)
{
if(isPrime[i])
{
prime[j++] = BigInteger.valueOf(i);
}
}
}

public static void main(String args[])
{
init();
List<BigInteger> P = new ArrayList<BigInteger>();
BigInteger MP = BigInteger.ZERO;
List<Node> ans = new ArrayList<Node>();
Scanner cin = new Scanner(new BufferedInputStream(System.in));
while(cin.hasNext())
{
BigInteger temp = cin.nextBigInteger();
if(temp.compareTo(MP) == 1)
{
MP = temp;
}
}
Map<Long, BigInteger> map = new HashMap<Long, BigInteger>();
Node origin = new Node();
origin.K = BigInteger.ONE;
origin.F = 1;
origin.N = 0;
map.put(origin.F, origin.K);
while(!queue.isEmpty())
{
Node u = queue.peek();
queue.remove();
BigInteger compare = map.get(u.F);
if(compare != null)
{
if(compare.compareTo(u.K) == -1)
{
continue;
}
}
for(int i=0;i<P.size();++i)
{
if(u.K.compareTo(P.get(i)) <= 0)
{
if(u.F > ans.get(i).F)
{
ans.get(i).F = u.F;
ans.get(i).K = u.K;
}
else if(u.F == ans.get(i).F)
{
if(u.K.compareTo(ans.get(i).K) == -1)
{
ans.get(i).K = u.K;
}
}
}
}
for(int i=0;i<u.N;++i)
{
Node v = new Node();
v.K = u.K.multiply(prime[i]);
if(v.K.compareTo(MP) <= 0)
{
v.F = u.F / (u.A[i] + 1) * (u.A[i] + 2);
v.N = u.N;
for(int j=0;j<u.N;++j)
{
v.A[j] = u.A[j];
}
++ v.A[i];
boolean flag = true;
compare = map.get(v.F);
if(compare != null)
{
if(compare.compareTo(v.K) <= 0)
{
flag = false;
}
else
{
map.remove(v.F);
}
}
if(flag)
{
map.put(v.F, v.K);
}
}
}
Node v = new Node();
v.K = u.K.multiply(prime[u.N]);
if(v.K.compareTo(MP) <= 0)
{
v.F = u.F * 2;
v.N = u.N + 1;
for(int i=0;i<u.N;++i)
{
v.A[i] = u.A[i];
}
++ v.A[u.N];
boolean flag = true;
compare = map.get(v.F);
if(compare != null)
{
if(compare.compareTo(v.K) <= 0)
{
flag = false;
}
else
{
map.remove(v.F);
}
}
if(flag)
{
map.put(v.F, v.K);
}
}
}
for(int i=0;i<ans.size();++i)
{
System.out.println(ans.get(i).K.toString() + " " + ans.get(i).F); //第一个数为满足因子个数最多的K，第二个数为K的因子个数
}
}
}

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