【蓝桥杯算法】Java的基础API

1. BigInteger 的使用

1.1. 判素数

package 模板;

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

public class 判素数 {
    static Scanner in = new Scanner(System.in);

    public static void main(String[] args) {
        int q = in.nextInt();
        while (q-- > 0) {
            BigInteger a = new BigInteger(in.next());
            if (a.isProbablePrime(20)) {
                System.out.println(a);
            } else {
                System.out.println(a.nextProbablePrime());
            }
        }
    }
}

1.2. 快速幂

package 模板;

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

public class 快速幂 {
    static Scanner in = new Scanner(System.in);

    public static void main(String[] args) {
        BigInteger b = new BigInteger(in.next());
        BigInteger p = new BigInteger(in.next());
        BigInteger k = new BigInteger(in.next());

        System.out.println(b.modPow(p, k));
    }
}

1.3. 求逆元

package 模板;

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

public class 逆元 {
    static Scanner in = new Scanner(System.in);

    public static void main(String[] args) {
        int q = in.nextInt();
        while (q-- > 0) {
            BigInteger a = new BigInteger(in.next());
            BigInteger b = new BigInteger(in.next());
            System.out.println(a.modInverse(b));
        }
    }
}

2. Arrays

1. 直接对于 int 对象排序使用的是快排
2. 对于 Integer 对象排序使用的是归并排序