洛谷入门题P1008、P1035、P1423、P1424、P1980题解（Java语言描述）

P1008题目描述

P1008题目链接

P1008题解

public class Main {
    private static byte[] arr = new byte[9];

    public static void main(String[] args) {
        for (int i = 123; i < 333; i++) {
            arr = new byte[9];
            int two = 2*i, three = 3*i;
            if (judge(i) && judge(two) && judge(three)) {
                System.out.println(i + " " + two + " " + three);
            }
        }
    }

    private static boolean judge(int i) {
        int a = i / 100;
        int b = (i % 100) / 10;
        int c = i - a*100 - b*10;
        if (b == 0 || c == 0 || a == b || a == c || b == c || arr[a-1] == 1 || arr[b-1] == 1 || arr[c-1] == 1) {
            return false;
        }
        arr[a-1] = arr[b-1] = arr[c-1] = 1;
        return true;
    }
}

本题答案：

192 384 576
219 438 657
273 546 819
327 654 981

P1035题目描述

P1035题目链接

P1035题解

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int k = scanner.nextInt();
        int n = 1;
        double sum = 0.0;
        while (sum <= k) {
            sum += (double)1/n;
            if (sum <= k) {
                n++;
            }
        }
        System.out.println(n);
        scanner.close();
    }
}

P1423题目描述

P1423题目链接

P1423题解

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double range = scanner.nextDouble();
        double sum = 0.0;
        int step = 0;
        double nextStep = 2.0;
        while (sum < range) {
            sum += nextStep;
            nextStep *= 0.98;
            step++;
        }
        System.out.println(step);
        scanner.close();
    }
}

P1424题目描述

P1424题目链接

P1424题解

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int fromDay = scanner.nextInt(), dayNum = scanner.nextInt();
        int weekdayNum = dayNum / 7 * 5;
        int leftNum = dayNum % 7;
        if (leftNum > 0) {
            if (leftNum + fromDay == 7 || fromDay == 7) {
                leftNum -= 1;
            } else if (leftNum + fromDay >= 8) {
                leftNum -= 2;
            }
        }
        System.out.println((weekdayNum + leftNum) * 250);
        scanner.close();
    }
}

P1980题目描述

P1980题目链接

P1980题解

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int toNum = scanner.nextInt(), searchNum = scanner.nextInt();
        int[] array = new int[10];
        for (Integer i = 1; i <= toNum; i++) {
            for (char c : i.toString().toCharArray()) {
                array[c-48]++;
            }
        }
        System.out.println(array[searchNum]);
        scanner.close();
    }
}

没啥可讲解的，很容易就完事