HDU-4919-数学推导加Java大数
2016-07-08 22:34
555 查看
题目链接
题目大意:通过给出的公式,已知n求f(n)
最后总结得出公式 :
n=2k时f(n)=2*f(k)+2*f(k-1)+4*k-4
n=2k+1时f(n)=4*f(k)+6k
最后用Java大数轻松写完
import sun.awt.image.PixelConverter;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
/**
* Created by dell on 2016/7/7.
*/
public class Main {
BigInteger x0=new BigInteger("0");
BigInteger x1=new BigInteger("1");
BigInteger x2=new BigInteger("2");
BigInteger x3=new BigInteger("3");
BigInteger x4=new BigInteger("4");
BigInteger x5=new BigInteger("5");
BigInteger x6=new BigInteger("6");
Map<BigInteger,BigInteger>vis=new HashMap<BigInteger, BigInteger>();
BigInteger dfs(BigInteger n) {
if(vis.get(n)!=null) {
return vis.get(n);
}
BigInteger k=n.divide(x2);
BigInteger k1=k.subtract(x1);
BigInteger ans=x0;
if(n.mod(x2).compareTo(x1)==0) {
ans=dfs(k).multiply(x4).add(k.multiply(x6));
vis.put(n,ans);
return ans;
}
else {
ans=dfs(k).multiply(x2).add(dfs(k1).multiply(x2).add(k.multiply(x4).subtract(x4)));
vis.put(n,ans);
return ans;
}
}
void work() {
Scanner cin = new Scanner(System.in);
vis.put(x2,x0);
vis.put(x3,x6);
vis.put(x4,x4);
BigInteger n;
while(cin.hasNext()) {
n=cin.nextBigInteger();
System.out.println(dfs(n));
}
}
public static void main(String[] args){
Main e=new Main();
e.work();
}
}
题目大意:通过给出的公式,已知n求f(n)
最后总结得出公式 :
n=2k时f(n)=2*f(k)+2*f(k-1)+4*k-4
n=2k+1时f(n)=4*f(k)+6k
最后用Java大数轻松写完
import sun.awt.image.PixelConverter;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
/**
* Created by dell on 2016/7/7.
*/
public class Main {
BigInteger x0=new BigInteger("0");
BigInteger x1=new BigInteger("1");
BigInteger x2=new BigInteger("2");
BigInteger x3=new BigInteger("3");
BigInteger x4=new BigInteger("4");
BigInteger x5=new BigInteger("5");
BigInteger x6=new BigInteger("6");
Map<BigInteger,BigInteger>vis=new HashMap<BigInteger, BigInteger>();
BigInteger dfs(BigInteger n) {
if(vis.get(n)!=null) {
return vis.get(n);
}
BigInteger k=n.divide(x2);
BigInteger k1=k.subtract(x1);
BigInteger ans=x0;
if(n.mod(x2).compareTo(x1)==0) {
ans=dfs(k).multiply(x4).add(k.multiply(x6));
vis.put(n,ans);
return ans;
}
else {
ans=dfs(k).multiply(x2).add(dfs(k1).multiply(x2).add(k.multiply(x4).subtract(x4)));
vis.put(n,ans);
return ans;
}
}
void work() {
Scanner cin = new Scanner(System.in);
vis.put(x2,x0);
vis.put(x3,x6);
vis.put(x4,x4);
BigInteger n;
while(cin.hasNext()) {
n=cin.nextBigInteger();
System.out.println(dfs(n));
}
}
public static void main(String[] args){
Main e=new Main();
e.work();
}
}
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