2020.9.28

一、今日学习内容：、

今天研究的一个算法是随机生成三十道一百以内的加减法另外还有九九乘法表内的乘除法：

//20194021 xin1905-2 marongrong
package Sizeyunsuan;
/**
 * 30道100以内四则运算
 * 
 * */
public class Random {

    public static int getRandom( int n, int m)
         {
        //产生n->m的随机数
                return (int) (Math.random() * (m - n) + n);
         }
    
    public static char getCharRandom()
    {
        //随机产生四种运算符
        char sign = 0;
        int Sn;
        Sn = getRandom(1,5);
        switch(Sn)
        {
            case 1:sign = '+' ;break;
            case 2:sign = '-' ;break;
            case 3:sign = '×' ;break;
            case 4:sign = '÷' ;break;
        }
        return sign;
    }
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub

         int i = 0;
         do
         {
             int  x = (int) (Math.random() * (100 - 1 )+ 1);  //产生1-100的随机数
             int  y = (int) (Math.random() * (100 - 1 )+ 1);  //产生1-100的随机数
             char sign = getCharRandom();
             /*
              * 判断乘法的范围*/
             switch(sign)
             {
             case '+':
                 System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );
                 i++;break;
             case '-':
                 if(x < y)                        //判断减数与被减数的大小关系
                 {
                     int temp;
                     temp = x;
                     x = y;
                     y = temp;
                 }
                 System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );
                 i++;break;
             case '×':
             {
                 x = (int) (Math.random() * (10 - 1 )+ 1);//新生成x,y<9的随机数
                 y = (int) (Math.random() * (10 - 1 )+ 1);
                 
                     System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );    
                     i++;
             };break;
             case '÷':
                 do                                             //循环生成除法
                 {
                     y = (int) (Math.random() * (10 - 1 )+ 1);
                     x = (int) (Math.random() * (9*y - 1 )+ 1);
                                            
                 }
                while(x % y != 0) ;
                System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );
                i++;break;
                 }
            /* if(sign == '×')
             {
                 x = (int) (Math.random() * (10 - 1 )+ 1);//新生成x,y<9的随机数
                 y = (int) (Math.random() * (10 - 1 )+ 1);
                 
                     System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );    
                     i++;
             }*/
            /*
             * 加减法判断*/     
            /* if(sign == '+' || sign == '-')
             {
                 if(x < y)                        //判断减数与被减数的大小关系
                 {
                     int temp;
                     temp = x;
                     x = y;
                     y = temp;
                 }
                 System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );
                 i++;
             }*/
             
             /*
              * 除法判断*/
            /* if(sign == '÷')
             {
                do                                             //循环生成除法
                 {
                     y = (int) (Math.random() * (10 - 1 )+ 1);
                     x = (int) (Math.random() * (9*y - 1 )+ 1);
                                            
                 }
                while(x % y != 0) ;
                System.out.println( "("+ (i+1) +")"+ x + " " + sign + " " + y + "="     );
                i++;

             }*/
        }
        while(i<30);
｝