“蓝桥杯”练习系统练习题答案（自己做的）

题目来源：

蓝桥杯练习系统（写博客日期为2019.3.23，所以可能读者看到的时候，更新了新的题）

这里只提供每道题的我的解题代码，仅供参考。这里不会写解题思路和详解，如果有需要的话，请留言给我，我会在留言区回复。vip题目来源dotcpp（顺序跟练习系统一样，只不过我没有vip，所以在dotcpp网站中看题并解题）。

试题集截图： 

 

入门训练：

1-1  BEGIN-1  A+B问题

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        System.out.println(a+b);
    }
}

1-2  BEGIN-2  序列求和

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        double n = in.nextInt();
        double s = (1 + n) / 2;
        double t = s * n;
        System.out.println((long)t);
    }
}

1-3  BEGIN-3  圆的面积

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        final double PI = 3.14159265358979323;
        double a = in.nextInt();
        double c = a*a*PI;
        System.out.printf("%.7f", c);
    }
}

1-4  BEGIN-4  Fibonacci数列

public class Main {
    public static void main(String[] ars){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        if(n < 3){
            System.out.println(1);
        }else {
            int[] a = new int[n + 1];
            a[1] = 1 % 10007;
            a[2] = 1 % 10007;
            for (int i = 3; i <= n; i++) {
                a[i] = (a[i - 1] + a[i - 2]) % 10007;
            }
            System.out.println(a[n]);
        }
    }
}

基础练习：

2-1  BASIC-1  闰年判断

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int y = in.nextInt();
        if((y%4 == 0 && y%100 != 0) || (y%400 == 0)){
            System.out.println("yes");
        }else {
            System.out.println("no");
        }
    }
}

2-2  BASIC-2  01字串

public class Main {
    public static void main(String[] args){
        for(int i=0; i<32; i++) {
            String str = Integer.toBinaryString(i);
            System.out.printf("%05d", Integer.valueOf(str));
            System.out.println();
        }
    }
}

2-3  BASIC-3  字母图形

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();
        String s = "BCDEFGHIJKLMNOPQRSTUVWXYZ";
        StringBuilder str = new StringBuilder(s);
        str = str.reverse();
        str.append("A");
        str.append(s);
        int a = str.indexOf("A");
        int b = a+m;
        for(int i=0; i<n; i++){
            System.out.println(str.substring(a, b));
            a--;
            b--;
        }
    }
}

2-4  BASIC-4  数列特征

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] s = new int[n];
        for(int i=0; i<n; i++){
            s[i] = in.nextInt();
        }
        int max = s[0];
        int min = s[0];
        int sum = 0;
        for(int j=0; j<s.length; j++){
            if(s[j] > max){
                max = s[j];
            }
            if(s[j] < min){
                min = s[j];
            }
            sum = sum + s[j];
        }
        System.out.println(max);
        System.out.println(min);
        System.out.println(sum);
    }
}

2-5  BASIC-5  查找整数

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] s = new int[n];
        for(int i=0; i<n; i++){
            s[i] = in.nextInt();
        }
        int a = in.nextInt();
        in.close();
        int count = 0;
        for(int j=0; j<s.length; j++){
            if(s[j] == a){
                count = j+1;
                break;
            }
        }
        if(count == 0){
            System.out.println(-1);
        }else {
            System.out.println(count);
        }
    }
}

2-6  BASIC-6  杨辉三角形

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[][] a = new int[n][n];
        if(n == 1){
            System.out.println(1);
        }else{
            a[0][0] = 1;
            for(int i=1; i<n; i++){
                a[i][0] = 1;
                a[i][i] = 1;
                if(n != 2){
                    for(int j=1; j<=i-1; j++){
                        a[i][j] = a[i-1][j-1] + a[i-1][j];
                    }
                }
            }
        }

        // 显示
        for(int i=0; i<n; i++){
            for(int j=0; j<=i; j++){
                System.out.print(a[i][j]);
                if(i!=j){
                    System.out.print(' ');
                }
            }
            System.out.println();
        }
    }
}

2-7  BASIC-7  特殊的数字

public class Main {
    public static void main(String[] args){
        for(int dd=100; dd<=999; dd++){
            String data = dd + "";
            char d0 = data.charAt(0);
            char d1 = data.charAt(1);
            char d2 = data.charAt(2);
            double sum1 = Math.pow((d0-'0'), 3) + Math.pow((d1-'0'), 3) + Math.pow((d2-'0'), 3);
            if((int)sum1 == dd){
                System.out.println(dd);
            }
        }
    }
}

2-8  BASIC-8  回文数

public class Main {
    public static void main(String[] args){
        StringBuilder a = new StringBuilder();
        for(int i=1; i<=9; i++){
            for(int j=0; j<=9; j++){
                a.append(i);
                a.append(j);
                a.append(j);
                a.append(i);
                System.out.println(a.toString());
                a.delete(0, a.length());
            }
        }
    }
}

2-9  BASIC-9  特殊回文数 

2-9-1  解法一

import java.util.Scanner;
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        for(int i=10000; i<=999999; i++){
            String data = "" + i;
            int sum = 0;
            for(int k=0; k<data.length(); k++){
                sum = sum + (data.charAt(k)-'0');
            }
            int len = data.length();
            int count = len/2;
            // 计算相等的个数，如果是2，3则满足
            StringBuilder flag = new StringBuilder();
            for(int j=0; j<count; j++){
                if(data.charAt(j) == data.charAt(len-j-1)){
                    flag.append(1);
                }else{
                    flag.append(0);
                }
            }
            if((flag.toString().equals("111") || flag.toString().equals("11")) && (n == sum)){
                System.out.println(i);
            }
            else{
                continue;
            }
        }
    }
}

2-9-2  解法二

import java.util.Scanner;

public class Main {
    public static void f5(int n){
        /* 五位数处理代码 */
        StringBuilder anser1 = new StringBuilder();
        // 测试第1位的值
        for(int i=1; i<=9; i++){
            // 测试第2位的值
            for(int j=0; j<=9; j++){
                // 计算第3位的值
                int third_number = n - 2*i - 2*j;
                if(third_number>=0 && third_number<=9){
                    anser1.append(i);
                    anser1.append(j);
                    anser1.append(third_number);
                    anser1.append(j);
                    anser1.append(i);
                    System.out.println(anser1);
                    anser1.delete(0, anser1.length());
                }else{
                    continue;
                }
            }
        }
    }

    public static void f6(int n){
        /* 六位数处理代码 */
        StringBuilder anser2 = new StringBuilder();
        // temp: 前三位相加的值
        int temp = n/2;
        // 测试第1位的值
        for(int i=1; i<=9; i++){
            // 测试第2位的值
            for(int j=0; j<=9; j++){
                // 计算第3位的值
                int third_number2 = temp-i-j;
                if(third_number2>=0 && third_number2<=9){
                    anser2.append(i);
                    anser2.append(j);
                    anser2.append(third_number2);
                    anser2.append(third_number2);
                    anser2.append(j);
                    anser2.append(i);
                    System.out.println(anser2);
                    anser2.delete(0, anser2.length());
                }else{
                    continue;
                }
            }
        }
    }

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        f5(n);
        // 偶数才可能是6位
        if(n%2==0){
            f6(n);
        }
    }
}

2-10  BASIC-10  十进制转十六进制

import java.util.Scanner;

public class Main {
    public static char f(long a){
        char temp = ' ';
        if(a<=9){
            temp = (char)(a+48);
        }else {
            switch ((int) a) {
                case 10:
                    temp = 'A';
                    break;
                case 11:
                    temp = 'B';
                    break;
                case 12:
                    temp = 'C';
                    break;
                case 13:
                    temp = 'D';
                    break;
                case 14:
                    temp = 'E';
                    break;
                case 15:
                    temp = 'F';
                    break;
            }
        }
//        System.out.println(temp);
        return temp;
    }

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        long a = in.nextLong();
        StringBuilder ss = new StringBuilder();
        if(a == 0){
            ss.append(0);
        }else {
            while (a != 0) {
                long number = a % 16;
                char s = f(number);
                ss.append(s);
                a = a / 16;
            }
        }
        System.out.println(ss.reverse().toString());
    }
}

2-11  BASIC-11  十六进制转十进制

import java.util.*;

public class Main {

    public static int f(char a){
        int x=0;
        if(a>='0' && a<='9'){
            x = a-'0';
        }else{
            switch (a){
                case 'A': x = 10;break;
                case 'B': x = 11;break;
                case 'C': x = 12;break;
                case 'D': x = 13;break;
                case 'E': x = 14;break;
                case 'F': x = 15;break;
                default:break;
            }
        }
        return x;
    }

    public static void h(String str){
        int len = str.length();
        double x = 0;
        for(int i=0; i<len; i++){
            int value = f(str.charAt(i));
            x = value*Math.pow(16, len-1-i) + x;
        }
        System.out.println((long)x);
    }

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        String a = in.next();
        in.close();
        h(a);
    }
}

2-12  BASIC-12  十六进制转八进制

import java.util.Scanner;

public class Main {
    public static String f(String s){
        int len = s.length();
        StringBuilder str = new StringBuilder();
        for(int i=0; i<len; i++){
            switch (s.charAt(i)){
                case '0': str.append("0000");break;
                case '1': str.append("0001");break;
                case '2': str.append("0010");break;
                case '3': str.append("0011");break;
                case '4': str.append("0100");break;
                case '5': str.append("0101");break;
                case '6': str.append("0110");break;
                case '7': str.append("0111");break;
                case '8': str.append("1000");break;
                case '9': str.append("1001");break;
                case 'A': str.append("1010");break;
                case 'B': str.append("1011");break;
                case 'C': str.append("1100");break;
                case 'D': str.append("1101");break;
                case 'E': str.append("1110");break;
                case 'F': str.append("1111");break;
                default: break;
            }
        }
        return str.toString();
    }

    public static void g(String str){
        int len = str.length();
        StringBuilder a = new StringBuilder();
        for(int i=0; i<len; i+=3){
            int temp = (str.charAt(i)-'0')*4+(str.charAt(i+1)-'0')*2+(str.charAt(i+2)-'0');
            a.append(temp);
        }
        System.out.println(a.toString().replaceFirst("^0*", ""));
    }

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String[] a = new String[n];
        for(int i=0; i<n; i++){
            a[i] = in.next();
        }
        in.close();
        for(int j=0; j<n; j++){
            String str2 = f(a[j]);
            int len2 = str2.length();
            if(len2 % 3 == 1){str2 = "00" + str2;}
            else if(len2 % 3 == 2){str2 = "0" + str2;}
            g(str2);
        }

    }
}

2-13  BASIC-13  数列排序

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int i=0; i<n; i++){
            a[i] = in.nextInt();
        }
        for(int j=0; j<n-1; j++){
            for(int k=j+1; k<n; k++){
                if(a[j]>a[k]){
                    int tt = a[k];
                    a[k] = a[j];
                    a[j] = tt;
                }
            }
        }
        for(int j=0; j<n; j++){
            System.out.print(a[j]);
            if(j != n-1){
                System.out.print(" ");
            }
        }
    }
}

未完待续。。。（更新于2019.3.23）