JAVA大数操作

大数据操作指的是数字非常大，大到已经超过了整个数据类型的保存范围，需要使用对象的形式进行操作。

一、BigInteger

BigInteger表示大的整型数据

import java.math.BigInteger;public class BigIntegers {public static void main(String[] args) {String num1 = "999999999999999999999999999999";String num2 = "999999999999999999999999999998";BigInteger big1 = new BigInteger(num1);BigInteger big2 = new BigInteger(num2);System.out.println("加法操作:" + big1.add(big2));System.out.println("减法操作:" + big1.subtract(big2));System.out.println("乘法操作:" + big1.multiply(big2));BigInteger result[] = big1.divideAndRemainder(big2);System.out.println("相除后的商是:" + result[0]);System.out.println("相除后的余数是:" + result[1]);}}

二、BigDecimal

BigDecimal类的主要功能是进行小数的大数计算，而且最重要的是可以精确到指定的四舍五入位数。四舍五入需要用到如下方法：

public BigDecimal divide(BigDecimal divisor, int scale, RoundingMode roundingMode)

1.divisor：此BigDecimal要除以的值

2.scale：要返回的BigDecimal商的标度

3.roundingMode：要应用的舍入模式。------ROUND_HALF_UP

import java.math.BigDecimal;class MyMath{public static double add(String num1, String num2){BigDecimal big1 = new BigDecimal(num1);BigDecimal big2 = new BigDecimal(num2);return big1.add(big2).doubleValue();}public static double sub(String num1, String num2){BigDecimal big1 = new BigDecimal(num1);BigDecimal big2 = new BigDecimal(num2);return big1.subtract(big2).doubleValue();}public static double mul(String num1, String num2){BigDecimal big1 = new BigDecimal(num1);BigDecimal big2 = new BigDecimal(num2);return big1.multiply(big2).doubleValue();}public static double round(double num, int scale){BigDecimal bd1 = new BigDecimal(num);BigDecimal bd2 = new BigDecimal(1);return bd1.divide(bd2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();}public static double div(String num1, String num2, int scale){BigDecimal bd1 = new BigDecimal(num1);BigDecimal bd2 = new BigDecimal(num2);return bd1.divide(bd2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();}}public class BigIntegers {public static void main(String[] args) {String num1 = "12345.6789";String num2 = "3333.23443";System.out.println("加法操作:" + MyMath.round(MyMath.add(num1, num2), 2));System.out.println("减法操作:" + MyMath.round(MyMath.sub(num1, num2), 2));System.out.println("乘法操作:" + MyMath.round(MyMath.mul(num1, num2), 2));System.out.println("除法操作:" + MyMath.div(num1, num2, 2));}}

OJ大数问题：

1.http://acm.hdu.edu.cn/showproblem.php?pid=1002

import java.math.BigInteger;import java.util.Scanner;public class Main{    public static void main(String[] args){        Scanner scan = new Scanner(System.in);        while(scan.hasNextInt()){            int ncase = scan.nextInt();            for(int i = 1; i <= ncase; i++){                BigInteger a = scan.nextBigInteger();                BigInteger b = scan.nextBigInteger();                System.out.println("Case " + i + ":");                System.out.println(a + " + " + b + " = " + a.add(b));                if(i != ncase){                    System.out.println();                }            }        }    }}

2.http://acm.hdu.edu.cn/showproblem.php?pid=1042

import java.math.BigInteger;import java.util.Scanner;public class Main{    public static void main(String[] args){        Scanner scan = new Scanner(System.in);        while(scan.hasNextInt()){            int num = scan.nextInt();            BigInteger bg = BigInteger.ONE;            for(int i = 1; i <= num; i++){                bg = bg.multiply(BigInteger.valueOf(i));            }            System.out.println(bg);        }    }}

3.http://acm.hdu.edu.cn/showproblem.php?pid=1047

import java.math.BigInteger; import java.util.Scanner;   public class Main{     public static void main(String[] args) {         int n;         BigInteger tmp, res;         boolean flag = false;         Scanner cin = new Scanner(System.in);         cin.hasNextInt();         n = cin.nextInt();         for (int i = 0; i < n; i++) {             if (flag)                 System.out.println();             flag = true;             res = BigInteger.ZERO;             while (cin.hasNextBigInteger()) {                 tmp = cin.nextBigInteger();                 if (tmp.intValue() == 0)                     break;                 res = res.add(tmp);             }             System.out.println(res);         }     } } 

4.http://acm.hdu.edu.cn/showproblem.php?pid=1063

import java.math.BigDecimal;import java.util.Scanner;public class Main{public static void main(String[] args) {BigDecimal result;Scanner scan = new Scanner(System.in);while(scan.hasNext()){BigDecimal bd = scan.nextBigDecimal();int n = scan.nextInt();result = bd.pow(n);String str = result.stripTrailingZeros().toPlainString();if(str.charAt(0) == '0'){System.out.println(str.substring(1));}else{System.out.println(str);}}}}

5.http://acm.hdu.edu.cn/showproblem.php?pid=1753

import java.math.BigDecimal;import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scan = new Scanner(System.in);while(scan.hasNext()){BigDecimal num1 = scan.nextBigDecimal();BigDecimal num2 = scan.nextBigDecimal();BigDecimal sum = num1.add(num2);System.out.println(sum.stripTrailingZeros().toPlainString());}}}

6.http://acm.hdu.edu.cn/showproblem.php?pid=1715

import java.math.BigInteger;import java.util.Scanner;public class Main{public static void main(String[] args) {Scanner scan = new Scanner(System.in);BigInteger[]f = new BigInteger[1005];f[1] = BigInteger.ONE;f[2] = BigInteger.ONE;for(int i = 3; i < 1005; i++){f[i] = f[i-1].add(f[i-2]);}while(scan.hasNext()){int N = scan.nextInt();for(int i = 1; i <= N; i++){int index = scan.nextInt();System.out.println(f[index]);}}}}

7.http://acm.hdu.edu.cn/showproblem.php?pid=1316

import java.math.BigInteger;import java.util.Scanner;public class Main{public static void main(String[] args) {Scanner scan = new Scanner(System.in);BigInteger f[] = new BigInteger[100005];f[1] = BigInteger.ONE;f[2] = BigInteger.ONE.add(BigInteger.ONE);for (int i = 3; i < 10001; i++) {f[i] = f[i-1].add(f[i-2]);}while (scan.hasNext()) {BigInteger a = scan.nextBigInteger();BigInteger b = scan.nextBigInteger();BigInteger count = BigInteger.ZERO;if (a.equals(BigInteger.ZERO) && b.equals(BigInteger.ZERO)) {break;}else{for (int i = 1; i < 10001; i++) {if ((a.compareTo(f[i]) == 0 || a.compareTo(f[i]) == -1)&& (b.compareTo(f[i]) == 0 || b.compareTo(f[i]) == 1)) {count = count.add(BigInteger.ONE);}}System.out.println(count);}}}}