第五周上机练习

1.打印出所有的"水仙花数"，所谓"水仙花数"是指一个三位数，其各位数字立方和等于该数本身。例如：153是一个"水仙花数"，因为153=1的三次方＋5的三次方＋3的三次方。（知识点：循环语句、条件语句）

package xx;

public class pika {

    public static void main(String[] args) {
        int g,s,b,sum=0;
        for(int i = 100;i<=999;i++) {
            g=i%10;
            s=i/10%10;
            b=i/100;
            sum=g*g*g+s*s*s+b*b*b;
            if(sum==i) {
                System.out.print(i+" ");
            }
        }
    }
}

2.在控制台输出以下图形（知识点：循环语句、条件语句）

package xx;

import java.util.Scanner;

public class pika {

    public static void main(String[] args) {
        for(int i = 1; i <= 6; i++) {
            for(int j = 1; j <= i; j++) {
            System.out.print(j+" ");
        }
        System.out.println();
        }
    }
}

package xx;

import java.util.Scanner;

public class pika {

    public static void main(String[] args) {
        for(int i = 1; i <= 6; i++) {
            for(int j = 1; j <= 7-i; j++) {
            System.out.print(j+" ");
        }
        System.out.println();
        }
    }
}

package xx;

import java.util.Scanner;

public class pika {

    public static void main(String[] args) {
        for(int i = 1; i <= 6; i++) {
            for(int j = i; j >= 1; j--) {
            System.out.print(j+" ");
        }
        System.out.println();
        }
    }
}

package xx;

public class pika {

    public static void main(String[] args) {
        for (int a = 6; a >= 1; a--) {
            for (int i = 1; i <= 7 - a; i++) {
                System.out.print(" ");
            }
            for (int j = 1; j <= a; j++) {
                System.out.print(j);
            } 
            System.out.println(" ");
        }
    }
}

3. 输入年月日，判断这是这一年中的第几天（知识点：循环语句、条件语句）

package xx;

import java.util.Scanner;

public class pika {

    public static void main(String[] args) {
        int day=0;
        int month=0;
        int year=0;
        int sum=0;
        int leap;
        System.out.print("请输入年，月，日
");
        Scanner input = new Scanner(System.in);
        year=input.nextInt();
        month=input.nextInt();
        day=input.nextInt();
        switch(month)
        {
        case 1:
            sum=0;break;
        case 2:
            sum=31;break;
        case 3:
            sum=59;break;
        case 4:
            sum=90;break;
        case 5:
            sum=120;break;
        case 6:
            sum=151;break;
        case 7:
            sum=181;break;
        case 8:
            sum=212;break;
        case 9:
            sum=243;break;
        case 10:
            sum=273;break;
        case 11:
            sum=304;break;
        case 12:
            sum=334;break;
        default:
            System.out.println("data error");break;
            }
        sum=sum+day;
        if(year%400==0||(year%4==0&&year%100!=0))
            leap=1;
        else
            leap=0;
        if(leap==1 && month>2)
            sum++;
        System.out.println("It is the the day:"+sum);
    }
}

 4.由控制台输入一个4位整数，求将该数反转以后的数，如原数为1234，反转后的数位4321（知识点：循环语句、条件语句）

package xx;

import java.util.Scanner;

public class pika {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
           int a = sc.nextInt();
           if(a>999 && a<=9999){
               int gewei = a%10;
               int shiwei = a % 100 / 10;
               int baiwei = a%1000/100;
               int qianwei = a/1000;
               int sum = qianwei + baiwei*10 +shiwei*100 +gewei*1000;
               System.out.println(sum);
           }
           else{
               System.out.println("error");
           }
    }
}