迅雷2019秋招后台开发编程题题解

10 -61

28

package xunlei;

import java.util.Scanner;

/**
 * 有红黑两种颜色的方块积木，红色代表正数A，黑色代表负数B。选出17块积木排成一排，使得任意相邻7块积木之和都小于0。如何挑选才能使17块积木之和最大，最大值是多少？
 */
public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int i;
        for (i = 1; i <= 7; i++) {
            if (b * i + a * (7 - i) < 0) {
                break;
            }
        }
        int res;
        if ((7 - i) < 3) {
            res = (7 - i) * a + (3 - (7 - i)) * b + (b * i + a * (7 - i)) * 2;
        } else {
            res = 3 * a + (b * i + a * (7 - i)) * 2;
        }
        System.out.println(res);
    }
}

10

1

package xunlei;

import java.util.Scanner;

public class Main2 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long N = sc.nextLong();
        int m = (int) Math.floor(Math.sqrt(N));
        int res = 0;
        for (int i = 1; i < m + 1; i++) {
            for (int j = i + 1; j < m + 1; j += 2) {
                long c = j * j + i * i;
                if (c <= N && gcd(j, i) == 1) {
                    res++;
                } else if (c > N) {
                    break;
                }
            }
        }
        System.out.println(res);
    }

    private static int gcd(int x, int y) {
        return (x % y != 0) ? gcd(y, x % y) : y;
    }
}