JAVA大数类练手

今天突然看到了OJ上的大数类题目，由于学习了一点大数类的知识。果断水了6道题。。。。。。都是非常基础的。就当的练手的吧。

学到的只是一些大数类的基本操作。以后多做点这样的题，争取熟练运用水大数题。。。

大数阶乘

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=28

代码如下：

import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner cin = new Scanner(System.in);	
		int n = cin.nextInt();
		BigInteger ans = BigInteger.ONE;
		for(int i = 1; i <= n; ++i)
			ans = ans.multiply(BigInteger.valueOf(i));
		System.out.println(ans);
	}
}

棋盘覆盖

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=45

代码如下：

import java.math.BigInteger;
import java.util.*;
import java.io.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner in = new Scanner(System.in);
		int test = in.nextInt();
		while(test-- > 0)
		{
			int n;
			n = in.nextInt();
			BigInteger a = new BigInteger("4");
			for(int i = 1; i < n; ++i)
				a = a.multiply(BigInteger.valueOf(4));
			System.out.println(a.subtract(BigInteger.valueOf(1)).divide(BigInteger.valueOf(3)));
		}
	}
}

比较大小

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=73

代码如下：

import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner cin = new Scanner(System.in);	
		while(cin.hasNext())
		{
			BigInteger a = cin.nextBigInteger();
			BigInteger b = cin.nextBigInteger();
			if(a.equals(BigInteger.ZERO) && b.equals(BigInteger.ZERO))
				break;
			int flag = a.compareTo(b);
			if(flag == -1)
				System.out.println("ab");
		}
	}
}

大数加法

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=103

代码如下：

import java.math.BigInteger;
import java.util.*;
import java.io.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();		
		for(int i = 1; i <= n; ++i)
		{
			BigInteger a = in.nextBigInteger();
			BigInteger b = in.nextBigInteger();
			BigInteger ans = a.add(b);
			System.out.println("Case " + i + ":");
			System.out.println(a + " + " + b + " = " +ans);
		}
	}
}

递推求值

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=114

代码如下：

import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner cin = new Scanner(System.in);	
		BigInteger a[] = new BigInteger[100];
		while(cin.hasNext())
		{
			for(int i = 0; i <= 2; ++i)
				a[i] = cin.nextBigInteger();
			for(int i = 3; i <= 99; ++i)
				a[i] = a[i - 1].add(a[i - 2]).add(a[i - 3]);
			System.out.println(a[99]);
		}
	}
}

高精度幂

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=155

代码如下：

import java.io.*;
import java.math.BigDecimal;
import java.util.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner cin = new Scanner(System.in);	
		while(cin.hasNext())
		{
			BigDecimal ans = cin.nextBigDecimal();
			int n = cin.nextInt();
			String res = ans.pow(n).stripTrailingZeros().toPlainString(); //整数去掉小数点和后面的0
			if(res.startsWith("0")) //去掉前导0
			{
				res = res.substring(1);
			}
			System.out.println(res);
		}
	}
}