二柱子3.0

import java.util.Random;
import java.lang.Math;
import java.util.Scanner;

public class RandomCommon {

public static char operator(int se) {
char op=' ';
Random random = new Random();
int n = random.nextInt(100);
if(se==1)
{
switch(n%4)
{
case 0:op = '+';break;
case 1:op = '-';break;
case 2:op = '*';break;
case 3:op = '/';break;
}
}
if(se==2)
{
switch(n%2)
{
case 0:op = '+';break;
case 1:op = '-';break;
}
}
return op;
}

public static String problem(String str,int min,int max,int sumoperand,int chengchu) {
for(int i=2;i<sumoperand;i++)
{
int addnumber = (int)(Math.random()*(max-min)+min);
char c = operator(chengchu);
str = str + c + addnumber;
}
return str;
}

public static String Str0(int min,int max,int chengchu) {
int a = (int)(Math.random()*(max-min)+min);
int b = (int)(Math.random()*(max-min)+min);
char c = operator(chengchu);
String str0 = ""+a+c+b;
return str0;
}

public static int checkRepeat(String[] str,int n) {
int flag=0;
for(int i=0;i<n-1;i++)
{
if(str[i].equals(str[n]))
flag=1;//chongfu
}
return flag;
}

public static String timu(int min,int max,int sumoperand,int chengchu,String[] str1,int n) {
String str;
str1[n] = str = problem(Str0(min,max,chengchu),min,max,sumoperand,chengchu);
if(checkRepeat(str1,n)==0)
str = str;
else
str = timu(min,max,sumoperand,chengchu,str1,n);
return str;
}

public static void main(String[] args) {
int sumtitle;//出题个数
int sumoperand;//操作数个数
int min,max;
int chengchu;
Scanner sc = new Scanner(System.in);
System.out.println("请输入出题个数:");
sumtitle = sc.nextInt();
System.out.println("请输入操作数个数：");
sumoperand = sc.nextInt();
System.out.println("请输入任意数范围：");
System.out.println("min=");
min = sc.nextInt();
System.out.println("max=");
max = sc.nextInt();
System.out.println("是否需要乘除法：1.需要 2.不需要");
chengchu = sc.nextInt();
String[] str = new String[sumtitle];
for(int i=0;i<sumtitle;i++)
{
str[i] = timu(min,max,sumoperand,chengchu,str,i);
System.out.println(str[i]+"\n");
}
}//void()

}