Java 解决一些ACM中大数问题

 

大数中算术运算结果的首选标度

运算	结果的首选标度
加	max(addend.scale(), augend.scale())
减	max(minuend.scale(), subtrahend.scale())
乘	multiplier.scale() + multiplicand.scale()
除	dividend.scale() - divisor.scale()

 

 

Problem D: Integer Inquiry

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 59  Solved: 18
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Description

One of the first users of BIT's new supercomputer was Chip Diller. He extended his exploration of powers of 3 to go from 0 to 333 and he explored taking various sums of those numbers.

``This supercomputer is great,'' remarked Chip. ``I only wish Timothy were here to see these results.'' (Chip moved to a new apartment, once one became available on the third floor of the Lemon Sky apartments on Third Street.)

Input

The input will consist of at most 100 lines of text, each of which contains a single VeryLongInteger. Each VeryLongInteger will be 100 or fewer characters in length, and will only contain digits (no VeryLongInteger will be negative).

The final input line will contain a single zero on a line by itself.

Output

Your program should output the sum of the VeryLongIntegers given in the input.

Sample Input

123456789012345678901234567890
123456789012345678901234567890
123456789012345678901234567890
0

Sample Output

370370367037037036703703703670

HINT

大数相加,遇到输入0时输出结果,直到读到EOF(文件结尾)为止

代码:

import java.math.BigInteger;
import java.util.Scanner;
 
public class Main{
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        BigInteger a,b=new BigInteger("0");
        while(s.hasNext()){
            a=s.nextBigInteger();      //接收输入
            if(!(a.toString()==("0")))       //判定是否等于0
                b=b.add(a);                  
            if(a.toString()==("0")){
                System.out.println(b);
                b=new BigInteger("0");
            }
        }   
    }
}

Problem E: Product

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 38  Solved: 25
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Description

The problem is to multiply two integers X, Y. (0<=X,Y<10250)

Input

The input will consist of a set of pairs of lines. Each line in pair contains one multiplyer.

Output

For each input pair of lines the output line should consist one integer the product.

Sample Input

12
12
2
222222222222222222222222

Sample Output

144
444444444444444444444444

HINT

两个大数相乘,直到读到EOF(文件结尾)为止

代码:

import java.math.BigInteger;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        while(s.hasNext()){
            BigInteger a=s.nextBigInteger();
            BigInteger b=s.nextBigInteger();
            BigInteger c=a.multiply(b);
            System.out.println(c);
        }
    }
}

 

Problem F: Exponentiation

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 9  Solved: 6
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Description

Problems involving the computation of exact values of very large magnitude and precision are common. For example, the computation of the national debt is a taxing experience for many computer systems.

This problem requires that you write a program to compute the exact value of Rn where R is a real number ( 0.0 < R < 99.999) and n is an integer such that $0 < n le 25$.

Input

The input will consist of a set of pairs of values for R and n. The R value will occupy columns 1 through 6, and the n value will be in columns 8 and 9.

Output

The output will consist of one line for each line of input giving the exact value of Rn. Leading zeros and insignificant trailing zeros should be suppressed in the output.

Sample Input

95.123 12
0.4321 20
5.1234 15
6.7592  9
98.999 10
1.0100 12

Sample Output

548815620517731830194541.899025343415715973535967221869852721
.00000005148554641076956121994511276767154838481760200726351203835429763013462401
43992025569.928573701266488041146654993318703707511666295476720493953024
29448126.764121021618164430206909037173276672
90429072743629540498.107596019456651774561044010001
1.126825030131969720661201

HINT

大数a的n次幂,直到读到EOF(文件结尾)为止,其中忽略小数后面的0

代码:

import java.math.BigDecimal;
import java.util.Scanner;

public class Problem_F_Exponentiation {

    public static void main(String[] args) {
        Scanner s=new Scanner(System.in); 
        BigDecimal a;
        int b;
        String c;
        while(s.hasNext()){
            a=s.nextBigDecimal();
            b=s.nextInt();;
            a=a.pow(b).stripTrailingZeros();   //stripTrailingZeros将所得结果小数部分尾部的0去除
            c=a.toPlainString();              //toPlainString将所得大数结果不以科学计数法显示,并转化为字符串
            if(c.charAt(0)=='0')　　　　　　　　//用charAt()判定首位字符是否为0
                c=c.substring(1);
            System.out.println(c);
        }
    }
}

Problem G: If We Were a Child Again

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 7  Solved: 6
[Submit][Status][Web Board]

Description

The Problem

The first project for the poor student was to make a calculator that can just perform the basic arithmetic operations.

But like many other university students he doesn’t like to do any project by himself. He just wants to collect programs from here and there. As you are a friend of him, he asks you to write the program. But, you are also intelligent enough to tackle this kind of people. You agreed to write only the (integer) division and mod (% in C/C++) operations for him.

Input

Input is a sequence of lines. Each line will contain an input number. One or more spaces. A sign (division or mod). Again spaces. And another input number. Both the input numbers are non-negative integer. The first one may be arbitrarily long. The second number n will be in the range (0 < n < 231).

Output

A line for each input, each containing an integer. See the sample input and output. Output should not contain any extra space.

Sample Input

110 / 100
99 % 10
2147483647 / 2147483647
2147483646 % 2147483647

Sample Output

1
9
1
2147483646

HINT

大数求余与整除运算

代码:

import java.math.BigInteger;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        BigInteger a,b,t=new BigInteger("1");
        String c;
        while(s.hasNext()){
            a=s.nextBigInteger();
            c=s.next();
            b=s.nextBigInteger();
            if(c.equals("%"))   t=a.mod(b);      
            if(c.equals("/"))   t=a.divide(b);
            System.out.println(t);
        }
    }
}