快速幂+判断上的技巧

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        String b1 = Integer.toString(b, 2);
        long res = 1;
        long last = a;
        for (int i = b1.length() - 1; i >= 0; i--) {
            if(b1.charAt(i) == '1'){
                res *= last;
            }
            if(last > 1e9) {
                res = (long) 1e9 + 1;
                break;
            }
            if(res > 1e9) break;
            last = last * last;
        }
        if(res <= 1e9 && res >= 0)System.out.println(res);
        else System.out.println(-1);
    }
}

学习链接:快速幂算法 超详细教程-CSDN博客