java大數例題

對於一些公式簡單，運算比較大的題目時，可能需要用到java大數，下面介紹一下幾題簡單的java大數題

簡單的說一下，java交代碼的時候要把主類寫成Main，另外要把包名那一行給刪掉。

hdu1002 標準java大數a+b

import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
    void work() {
        Scanner cin = new Scanner(System.in);
        int n;
        n = cin.nextInt();
        BigInteger a, b, c;
        int kase = 0;
        for(int i = 1; i <= n; i++) {
            a = cin.nextBigInteger();
            b = cin.nextBigInteger();
            c = a.add(b);
            kase++;
            System.out.println("Case " + kase + ":");
            System.out.print(a);
            System.out.print(" + ");
            System.out.print(b);
            System.out.print(" = ");
            System.out.println(c);
            if(i != n) 
                System.out.println("");
        }
    }
    public static void main(String[] args){
        Main e = new Main();
        e.work();
    }
}

hdu1250 斐波那契大數版

import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
    void work() {
        Scanner cin = new Scanner(System.in);
        int n;
        BigInteger f1, f2, f3, f4, temp;
        while(cin.hasNext()) {
            f1 = BigInteger.ONE;
            f2 = f3 = f4 = temp = f1;
            n = cin.nextInt();
            if(n <= 4) {
                System.out.println(1);
                continue;
            }
            for(int i = 5; i <= n; i++) {
                temp = f1.add(f2.add(f3.add(f4)));
                f1 = f2;
                f2 = f3;
                f3 = f4;
                f4 = temp;
            }
            System.out.println(temp);
        }
    }
    public static void main(String[] args){
        Main e = new Main();
        e.work();
    }
}

hdu1042 大數階乘

import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
    void work() {
        Scanner cin = new Scanner(System.in);
        int n;
        while(cin.hasNext()) {
            n = cin.nextInt();
            BigInteger ans = new BigInteger("1");
            for(int i = 2; i <= n; i++) {
                ans = ans.multiply(BigInteger.valueOf(i));
            }
            System.out.println(ans);
        }
    }
    public static void main(String[] args){
        Main e = new Main();
        e.work();
    }
}

hdu1297 找規律+java大數類似斐波那契

遞推式子f(n)=f(n−1)+f(n−2)+f(n−4)

import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
    void work() {
        Scanner cin = new Scanner(System.in);
        BigInteger[] ans = new BigInteger[1111];
        ans[1] = BigInteger.valueOf(1);
        ans[2] = BigInteger.valueOf(2);
        ans[3] = BigInteger.valueOf(4);
        ans[4] = BigInteger.valueOf(7);
        for(int i = 5; i <= 1000; i++) {
            ans[i] = ans[i - 4].add(ans[i - 2].add(ans[i - 1]));
        }
        int n;
        while(cin.hasNext()) {
            n = cin.nextInt();
            System.out.println(ans[n]);
        }
    }
    public static void main(String[] args){
        Main e = new Main();
        e.work();
    }
}

hdu1753 a+b 大數有小數點版，去後導0

import java.math.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
    void work() {
        Scanner cin = new Scanner(System.in);
        BigDecimal a, b;
        while(cin.hasNext()) {
            a = cin.nextBigDecimal();
            b = cin.nextBigDecimal();
            System.out.println(a.add(b).stripTrailingZeros().toPlainString());
        }
    }
    public static void main(String[] args){
        Main e = new Main();
        e.work();
    }
}