王道入门50题答案

王道入门50题答案

345为进制转换和二进制的反码补码置换，其余不可见图片为代码运行结果，如若决定去王道培训，一下代码仅供参考，看不懂可评论或私信，会回复

1

java是跨平台的，但jvm不是跨平台的。

java编写的文件都会被编译成无关平台的字节码，任何一个平台的字节码都可以在JVM上执行，不同平台的JVM是不同的，jvm提供了相同的接口。

2

配置java环境可以方便使用命令行去编译运行java程序，不配置环境可以使用命令行可以编译代码，但需要在指定目录进行编译。

3

图片转存失败，请去查看其他攻略

图片转存失败，请去查看其他攻略

4

图片转存失败，请去查看其他攻略

5

图片转存失败，请去查看其他攻略

6

不能，因为byte的取值范围是-128~127 300大于此范围，可以把byte改为int或者把b强转为byte

7

a=a+0.1不能通过编译，因为a+0.1这个表达式，会把结果隐式转换为double类型，再赋值给一个int类型的变量会发生错误；a+=0.1可以通过编译，相当于int a=(int)(a+0.1)，会丢失精度。

8

不相等，因为其变量类型不同

9

使其整数按位与其减一，为0即为2的整次幂，不为0则不是，

10

字符串，+表示拼接，所以最终类型为字符串

11

结果为20 b=a+10 a=10 b=10+10=20

12

不合法：1myName(数字开头)、你好%(中文)、main、class(关键字)

合法：My_name、 Points、$points、 _sys_ta、 OK123、_23b#、— 3

13

类名：

1. demo 类名应该开头大写

2. test 类名应该开头大写

3. Student

4. Student_ 不能用_结束

5. program1 类名应该开头大写

6. MYDemo 应该使用驼峰命名法MyDemo

7. myDemo 类名应该开头大写

8. XueSheng

变量名：

1. age

2. nianLing

3. myName

4. _name 不能用_下划线开头

5. Variable

包名：

1. com.baidu

2. Com.Baidu 包名要用小写

3. bao.ceshi

14

注释的作用主要是提高代码的可读性，使其他人能更加轻松地理解和掌握代码。通常用于为语句、程序段、函数等提供解释或提示，帮助读者更好地理解代码的结构和目的。在编程语言中，注释不会影响程序的功能实现，因为编译系统会在编译过程中忽略注释部分。

15

1、导入包import java.util.Scanner;

2、通过new Scanner(System.in)创建一个Scanner，控制台会一直等待输入，直到敲回车键结束，把所输入的内容传给Scanner，作为扫描对象；

3、调用Scanner的nextLine()方法；

16

public class huiwen {public static void main(String[] args) {int sum =0;for(int i=10000;i<=99999;i++){String b = i+"";if (pd(b)){sum++;System.out.print(b+" ");}}}static boolean pd(String s){if (s.charAt(0)==s.charAt(4)&&s.charAt(1)==s.charAt(3)){return true;}return false;}
}

17

import java.util.Scanner;public class top2 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("Enter number");int n = sc.nextInt();switch (n){case 1:System.out.println("星期一");break;case 2:System.out.println("星期二");break;case 3:System.out.println("星期三");break;case 4:System.out.println("星期四");break;case 5:System.out.println("星期五");break;case 6:System.out.println("星期六");break;case 7:System.out.println("星期日");break;default:System.out.println("您输入的数字不正确，请重新输入");}sc.close();}
}

18

import java.util.Scanner;public class Top3 {public static void main(String[] args) {Scanner scan  = new Scanner(System.in);System.out.println("Enter number");int number = scan.nextInt();if (number >= 90) {System.out.println("优秀");}else if (number >= 80) {System.out.println("良好");}else if (number >= 70) {System.out.println("中等");}else if (number >= 60) {System.out.println("及格");}else if (number >= 0) {System.out.println("不及格");}else {System.out.println("输入错误，分数不能为负");}}
}

19

public class Top4 {public static void main(String[] args) {int a,b,c;for (int i = 100; i <= 999; i++) {a=i%10;b=i%100/10;c=i/100;if(a*a*a+b*b*b+c*c*c==i){System.out.println(i);}}}
}

20

public class Top5 {public static void main(String[] args) {boolean flag = true;//设置标记位for (int i = 100; i <= 200; i++){for (int j = 2; j <= Math.sqrt(i); j++){if (i%j==0){flag = false;//false说明不是素数}}if (flag){System.out.println(i);flag=true;}flag=true;//重置标记进入下轮循环}}
}

21

import java.util.Scanner;public class Top6 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int data = sc.nextInt();for (int i = 1; i <= data; i++) {for (int k = i + 1; k <= data; k++) {System.out.print(" ");}for (int j = 1; j <= 2 * i - 1; j++) {System.out.print("*");}System.out.println();}sc.close();}
}

22

public class Top7 {public static void main(String[] args) {for (int i = 1; i <= 9; i++) {for (int j = 1; j <= i; j++) {System.out.print(i + "*" + j + "=" + i*j + " ");}System.out.println();}}
}

23

public class Top8 {public static void main(String[] args) {for (int i = 1; i < 1000; i++) {int sum = 0;for (int j = 2; j < Math.sqrt(i); j++) {if (i % j == 0) {sum+=j+i/j;}}if (sum+1 == i) {//上边因数中排除了1System.out.println(i);}sum = 0;}}
}

24

public class top9 {public static void main(String[] args) {int[] arr = {1,2,3,4};int sum=0;for (int i = 0; i < arr.length; i++) {for (int j = 0; j < arr.length; j++) {if (arr[i] == arr[j]) {continue;}for (int k = 0; k < arr.length; k++) {if (arr[i] == arr[k]|| arr[j] == arr[k]) {continue;}System.out.println(arr[i]*100+arr[j]*10+arr[k]);sum++;}}}System.out.println(sum);}
}

25

import java.util.Scanner;public class Top10 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入一个正整数");String str = sc.nextLine();System.out.println(str.length());for (int i = str.length()-1; i >= 0; i--) {System.out.print(str.charAt(i));}}
}

26

import java.util.Scanner;public class Top11 {public static void main(String[] args) {int a=2,b=1,c;double ans=0;for (int i = 0; i < 20; i++) {c=a;ans+=(double) a/b;a=a+b;b=c;}System.out.println(ans);}
}

27

import java.util.Scanner;public class Top12 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("Enter number: ");int num = sc.nextInt();int sum = 0;for (int i = num; i >= 0; i--) {sum += i;}System.out.println(sum);}
}

28

import java.util.Scanner;public class Top13 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("Enter number: ");int num = sc.nextInt();int sum = 1;for (int i = num; i > 1; i--) {sum *= i;}System.out.println(sum);}
}

29

import java.util.Scanner;public class Top14 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int a=sc.nextInt();int b=sc.nextInt();int c=sc.nextInt();int max=0;int max1=0,max2=0;if(a>=b){if(a>=c){max=a;}else{max=c;}}else{if(b>=c){max=b;}else{max=c;}}System.out.println(+max);max1=a>b?a:b;max2=max1>c?max1:c;System.out.println(+max2);}
}

30

public class Top15 {public static void main(String[] args) {int count=0;for (int i = 1; i <= 10000; i++) {int a=(int)Math.sqrt(i+100);int b=(int)Math.sqrt(i+268);if (a*a==(i+100)||b*b==(i+268)){count++;System.out.println(i);}}System.out.println("一共有"+count+"个数");}
}

31

public class Top16 {public static void main(String[] args) {int a = 0;//存放奇数int b = 0;//存放偶数for (int i = 0; i < 100; i++) {if (i % 2 == 0) {b+=i;}else {a+=i;}}System.out.println("所有奇数的和为"+a);System.out.println("所有偶数的和为"+b);}
}

32

public class Top17 {public static void main(String[] args) {double height =100;double distance = 100;for (int i = 2; i <= 10; i++) {//首次已加height = height/2;distance = distance + height*2;}System.out.println(distance);System.out.println(height);}
}

33

import java.util.Scanner;public class Top18 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();if (n%9==0){int count=0;while (n>1){n/=9;count++;}System.out.println(count);}else {System.out.println(0);}}
}

34

import java.util.Scanner;public class Top19 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();if (n%2==0){System.out.println("这是一个偶数");}else {System.out.println("这是一个奇数");}}
}

35

import java.util.Scanner;public class tOP20 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();System.out.print(n+"=");int count = 0 ;for (int i = 2; i <= n; i++) {if (n % i == 0){//判断时候为因子count++;while (n%i ==0){//除掉其中质因数的倍数n = n/i;}if (count==1)System.out.print(i);else System.out.print("*"+i);}}}
}

36

import java.util.Arrays;
import java.util.Scanner;public class Top21 {public static void main(String[] args) {int[] arr = new int[3];Scanner sc = new Scanner(System.in);for (int i = 0; i < arr.length; i++) {arr[i] = sc.nextInt();}Arrays.sort(arr);for (int i = arr.length-1; i >=0 ; i--) {System.out.print(arr[i]+" ");}}
}

37

import java.util.Scanner;public class Top22 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int a = sc.nextInt(),b = sc.nextInt();int temp = a;a = b;b = temp;System.out.println(a+" "+b);}
}

38

import java.util.Scanner;public class Top23 {public static void main(String[] args) {for(int i=1;i<=10000;i++) {int p = i*i;String ptr = Integer.toString(p);String tpr = Integer.toString(i);String last = ptr.substring(ptr.length()-tpr.length());if(tpr.equals(last)) {System.out.println(i);}}}
}

39

public class Top24 {public static void main(String[] args) {int a = 20,b=0;int count =0;while (a>3){b=a/3;count +=b;a=a-b*3+b;}System.out.println(count);}
}

40

public class Top25 {public static void main(String[] args) {double a =56.7,b=0;int count=0;while (a>b){count++;b+=5;if (b>a)break;b-=3.5;}System.out.println(count);}
}

41

import java.util.Scanner;public class Top26 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int sum = 0;while (n>10) {sum += n%10;n/=10;}System.out.println(sum+n);}
}

42

public class Top27 {public static void main(String[] args) {int sum = 0;for (int i = 0; i < 100; i++) {if (i>=7&&i / 7 == 0 || i % 10 == 7) {continue;}System.out.print(i+" ");}}
}

43

import java.util.Scanner;public class Top28 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();double sum = 0;for (double i = 1; i <= n; i++) {if (n%2==i%2) {//同为奇数或者同为偶数sum+=1/i;}}System.out.println(sum);}
}

44

import java.util.Scanner;public class Top29 {public static void main(String[] args) {int[] arr = {31,29,31,30,31,30,31,31,30,31,30,31};Scanner sc = new Scanner(System.in);int year = sc.nextInt();int month = sc.nextInt();if(year%4==0&&year%100==0||year%400==0){if(month==2){System.out.println(year+"年的"+month+"月有"+28+"天");}}else {System.out.println(year+"年的"+month+"月有"+arr[month-1]+"天");}}
}

45

import java.util.Scanner;public class Top30 {public static void main(String[] args) {double a = (24+8+3)*0.8;double b = 16+8+3;System.out.println(a>b?b:a);}
}

46

import java.util.Scanner;public class Top31 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int[] arr = new int[n];arr[0] = 1;arr[1]=1;for (int i = 2; i < n; i++) {arr[i] =f(i+1);}for (int i = 0; i < n; i++) {System.out.print(arr[i] + " ");}}static int f(int a){if (a==1)return 1;if(a==2)return 1;return f(a-1)+f(a-2);}
}

47

import java.util.Scanner;public class Top32 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int k = sc.nextInt();System.out.println(f(n,k-1));}static int f(int i, int j){if (j==0)return i;return f(i+2,j-1);}
}

48

import java.util.Arrays;
import java.util.Scanner;public class Top33 {public static void main(String[] args) {int[] arr= new int[10];Scanner sc = new Scanner(System.in);for(int i=0;i<arr.length;i++){arr[i]= sc.nextInt();}Arrays.sort(arr);for(int i=0;i<arr.length;i++){System.out.print(arr[i]+" ");}}
}

49

import java.util.Scanner;public class Top34 {static int[] arr = {1,2,3,4,5,6,7,8,0};public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();for (int i = 0; i < arr.length; i++) {if (arr[i]  == n) {yd(i);arr[i] = n;break;}}for (int i = 0; i < arr.length; i++) {System.out.print(arr[i]+" ");}}public static void yd(int index) {for (int i = arr.length-1; i >=index ; i--) {arr[i] = arr[i-1];}}
}

50

import java.util.Scanner;public class Top35 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();//数组长度int[] arr = new int[n];for (int i = 0; i < n; i++) {arr[i] = sc.nextInt();}int max = 0, min = Integer.MAX_VALUE,temp = 0;for (int i = 0; i < n; i++) {if (arr[i] > max) {max = arr[i];}if (arr[i] < min) {min = arr[i];}}for (int i = 0; i < n; i++) {if (arr[i] == max) {temp = arr[i];arr[i] = arr[0];arr[0] = temp;}if (arr[i] == min) {temp = arr[i];arr[i] = arr[n-1];arr[n-1] = temp;}}for (int i = 0; i < n; i++) {System.out.print(arr[i] + " ");}}
}