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2013蓝桥杯题解

第一题：暴力枚举

本题采用暴力枚举的方法，结合排序和循环标签的技巧，来解决问题。

方法思路

代码解析

import java.util.Arrays;
public class Main {
    public static void main(String[] args) {
        outer: // 循环标签
        for (int i = 203891; i < 987654; i++) {
            String num = String.valueOf(i);
            char[] arr = num.toCharArray();
            Arrays.sort(arr);
            for (int j = 0; j < arr.length - 1; j++) {
                if (arr[j] == arr[j + 1]) continue outer;
            }
            long i_pow = (long)i * i;
            String pow_number = String.valueOf(i_pow);
            char[] arr_pow = pow_number.toCharArray();
            for (int j = 0; j < arr_pow.length; j++) {
                for (int k = 0; k < arr.length; k++) {
                    if (arr_pow[j] == arr[k]) continue outer;
                }
            }
            System.out.print(i);
        }
    }
}

第二题：模拟回文日期

方法思路

代码解析

import java.util.Scanner;
public class Main {
    static int[] days = new int[]{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int flag = 0;
        for (int date = n + 1; date <= 99999999; date++) {
            if (!check_valid(date)) continue;
            if (flag == 0 && check_palindrome(date)) {
                System.out.println(date);
                flag = 1;
            }
            if (check_AB(date)) {
                System.out.println(date);
                break;
            }
        }
    }
    private static boolean check_palindrome(int date) {
        String str = Integer.toString(date);
        StringBuffer sb = new StringBuffer(str.substring(4));
        if (str.startsWith(sb.reverse().toString())) {
            return true;
        }
        return false;
    }
    private static boolean check_AB(int date) {
        String str = Integer.toString(date);
        char[] arr = str.toCharArray();
        int a = str.charAt(0), b = str.charAt(1);
        if (a == b) return false;
        return arr[2] == a && arr[5] == a && arr[7] == a && arr[3] == b && arr[4] == b && arr[6] == b;
    }
    private static boolean check_valid(int date) {
        int year = date / 10000;
        int month = date % 10000 / 100;
        int day = date % 100;
        if (month == 0 || month > 12) return false;
        if (day == 0 || month != 2 && day > days[month]) return false;
        if (month == 2) {
            int leap = 0;
            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) leap = 1;
            if (day > 28 + leap) return false;
        }
        return true;
    }
}

第三题：递推问题

方法思路

代码解析

import java.util.Scanner;
public class Main {
    static final int N = 1000010;
    static int[] f = new int[N];
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        for (int i = 1; i <= n; i++) {
            f[i] = (f[i - 1] + k) % i;
        }
        System.out.print(f[n] + 1);
    }
}

第四题：数学递推

方法思路

代码解析

import java.util.Scanner;
public class Main {
    static final int N = 1000010;
    static int[] f = new int[N];
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        for (int i = 1; i <= n; i++) {
            f[i] = (f[i - 1] + k) % i;
        }
        System.out.print(f[n] + 1);
    }
}

以上是对各题的详细解答和代码解析。

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