JAVA大数在ACM中应用

1. HDU-1002

大数A+B

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

    public class Main {

        public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
            int T;
            T = in.nextInt();
            for(int cas = 1;cas <= T;cas++ )
            {
                System.out.println("Case "+cas+":");
                BigInteger a = in.nextBigInteger();
                BigInteger b = in.nextBigInteger();
                BigInteger c = a.add(b);
                System.out.println(a+" + "+b+" = "+c);
                if(cas!=T)System.out.println("");
            }
        }
    }

1. HDU-1042(https://cn.vjudge.net/problem/HDU-1042)

求N!

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int T;
        while(in.hasNext())
        {
            int n = in.nextInt();
            BigInteger ans = new BigInteger("1");
            for(int i=1;i<=n;i++)
            {
                BigInteger a=BigInteger.valueOf(i);
                ans = ans.multiply(a);
            }
            System.out.println(ans);
        }

    }
}

1. HDU - 1133
   公式:(m+n)!*(m-n+1)/(m+1)

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int cas = 0;
        while(in.hasNext())
        {
            cas++;
            int m = in.nextInt();
            int n = in.nextInt();
            if(n==0&&m==0)
            {
                break;
            }
            if(m<n)
            {
                System.out.println("Test #"+cas+":");
                System.out.println("0");
                continue;
            }
            BigInteger ans = new BigInteger("1");
            for(int i=1;i<=n+m;i++)
            {
                BigInteger a=BigInteger.valueOf(i);
                ans = ans.multiply(a);
            }
            BigInteger a=BigInteger.valueOf(m-n+1);
            ans = ans.multiply(a);
            a=BigInteger.valueOf(m+1);
            ans = ans.divide(a);
            System.out.println("Test #"+cas+":");
            System.out.println(ans);
        }
    }
}

1. HDU - 1250
   公式:F(1) = 1, F(2) = 1, F(3) = 1,F(4) = 1, F(n>4) = F(n - 1) + F(n-2) + F(n-3) + F(n-4)

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        BigInteger f[] = new BigInteger[10005];
        while(in.hasNext())
        {
            int n = in.nextInt();
            f[1] = BigInteger.valueOf(1);
            f[2] = BigInteger.valueOf(1);
            f[3] = BigInteger.valueOf(1);
            f[4] = BigInteger.valueOf(1);
            for(int i=5;i<=n;i++)
            {
                f[i]=f[i-1].add(f[i-2]).add(f[i-3]).add(f[i-4]);
            }
            System.out.println(f[n]);
        }
    }
}

HDU - 1297
f[i] = f[i - 1].add(f[i - 2]).add(f[i - 4]);

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        BigInteger f[] = new BigInteger[10005];
        //f[n] = f[n - 1] + f[n - 2] + f[n - 4]
        f[0] = BigInteger.valueOf(1);
        f[1] = BigInteger.valueOf(1);
        f[2] = BigInteger.valueOf(2);
        f[3] = BigInteger.valueOf(4);
        for(int i=4;i<=1000;i++)
        {
            f[i] = f[i - 1].add(f[i - 2]).add(f[i - 4]);
        }
        while(in.hasNext())
        {
            int n = in.nextInt();
            System.out.println(f[n]);
        }
    }
}

HDU - 1715

Fibonacci数列

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        BigInteger f[] = new BigInteger[10005];
        //f[n] = f[n - 1] + f[n - 2] + f[n - 4]
        f[0] = BigInteger.valueOf(0);
        f[1] = BigInteger.valueOf(1);
        for(int i=2;i<=1000;i++)
        {
            f[i] = f[i - 1].add(f[i - 2]);
        }

        int T;
        T = in.nextInt();
        for(int cas=1;cas<=T;cas++)
        {
            int n = in.nextInt();
            System.out.println(f[n]);
        }

    }
}

HDU - 1753

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        while(in.hasNext())
        {
            BigDecimal a  = in.nextBigDecimal();
            BigDecimal b  = in.nextBigDecimal();
            BigDecimal c  = a.add(b);
            c = c.stripTrailingZeros();
            String s=c.toPlainString();
            System.out.println(s);
        }

    }
}
/*
一个是 BigDecimal.stripTrailingZeros()
，作用是将BigDecimal转化为最简形式（去掉末尾多余的0或小数点）

还有 BigDecimal.toPlainString() ，
作用是将BigDecimal转为字符串，因为小数位数过多的话会被输出成科学计数法表示，
不希望那样的话就要用到这个方法；
 */

HDU - 1865

f[i] = f[i-1] + f[i-2]

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

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        BigInteger f[] = new BigInteger[1000];
        f[1] = BigInteger.valueOf(1);
        f[2] = BigInteger.valueOf(2);
        for(int i=3;i<=200;i++)
        {
            f[i] = f[i-1].add(f[i-2]);
        }
        int T;
        T = in.nextInt();
        for(int i=1;i<=T;i++)
        {
            String s = in.next();
            System.out.println(f[s.length()]);
        }

    }
}
/*
一个是 BigDecimal.stripTrailingZeros()
，作用是将BigDecimal转化为最简形式（去掉末尾多余的0或小数点）

还有 BigDecimal.toPlainString() ，
作用是将BigDecimal转为字符串，因为小数位数过多的话会被输出成科学计数法表示，
不希望那样的话就要用到这个方法；
 */