java写大数总结

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把一些涉及到大数的水题写了一番，以后遇到大数还是java大法方便啊。

HDU 1002

a+b大数版

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

HDU 1042

阶乘大数版

import java.math.BigInteger;import java.util.Scanner;public class Main {    int maxn = 10005;    void solve () {        Scanner cin = new Scanner(System.in);        int n;        while (cin.hasNext()) {            n = cin.nextInt ();            BigInteger ans = BigInteger.valueOf (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 work = new Main();        work.solve ();    }}

HDU 1250

斐波那契数列大数版

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

HDU 1297

f(n)=f(n−1)+f(n−2)+f(n−4)

import java.math.*;import java.util.*;public class Main {    void solve () {        Scanner cin = new Scanner(System.in);        BigInteger[] ans = new BigInteger[1001];        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-1].add (ans[i-2].add (ans[i-4]));        }        while (cin.hasNext ()) {            int n = cin.nextInt ();            System.out.println (ans[n]);        }    }    public static void main (String[] args) {        Main work = new Main();        work.solve ();    }}

HDU 1715

还是斐波那契数列

import java.math.BigInteger;import java.util.Scanner;public class Main {    void solve () {        Scanner cin = new Scanner(System.in);        int t = cin.nextInt ();        BigInteger f1, f2, f3;        for (int i = 0; i < t; i++) {            int n = cin.nextInt ();            f1 = BigInteger.valueOf (1);            f2 = BigInteger.valueOf (1);            f3 = BigInteger.valueOf (0);            if (n == 1 || n == 2) {                System.out.println ("1");                continue;            }            for (int j = 3; j <= n; j++) {                f3 = f1.add (f2);                f1 = f2;                f2 = f3;            }            System.out.println (f3);        }    }    public static void main (String[] args) {        Main work = new Main();        work.solve ();    }}

HDU 1753

高精度小数，要去掉末尾的后导0.

import java.math.*;import java.util.*;public class Main {    void solve () {        //BigInteger a, b, c;        Scanner cin = new Scanner(System.in);        BigDecimal a = BigDecimal.valueOf (0);        BigDecimal b = BigDecimal.valueOf (0);        while (cin.hasNext ()) {            a = cin.nextBigDecimal ();            b = cin.nextBigDecimal ();            System.out.println (a.add (b).stripTrailingZeros().toPlainString());        }    }    public static void main (String[] args) {        Main work = new Main();        work.solve ();    }}

HDU 1865

f(n)=f(n−1)+f(n−2)

import java.math.*;import java.util.*;public class Main {    void solve () {        BigInteger a, b, c;        Scanner cin = new Scanner(System.in);        int t = cin.nextInt ();        String s;        for (int l = 1; l <= t; l++) {            s = cin.next ();            int n = s.length ();            if (n == 1 || n == 2) {                System.out.println (n);                continue;            }            BigInteger f1 = BigInteger.valueOf (1);            BigInteger f2 = BigInteger.valueOf (2);            BigInteger f3 = BigInteger.valueOf (0);            for (int i = 3; i <= n; i++) {                f3 = f1.add (f2);                f1 = f2;                f2 = f3;            }            System.out.println (f3);        }    }    public static void main (String[] args) {        Main work = new Main();        work.solve ();    }}

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