四则运算题目程序

#include <stdlib.h>
#include<stdio.h>
#include <iostream.h>
#include <conio.h>
#include <time.h>
int main()
{
 int a = 0;
 int b = 0;
 int mode = 0;
 int c = 0;
 int result = 0;
 int score = 0;
 int i = 0;
    for(i=0;i<30;i++)
 {
    a = rand() % 100;
 b = rand() % 100; 
 mode = rand() % 4;     
 printf("%d", a);  
    switch(mode)       
 {         
 case 0:              
  printf("+ ");              
  result= a + b;        
  break;         
 case 1:               
  printf("- ");              
  result= a - b;              
  break;         
 case 2:              
  printf("x ");              
  result= a * b;             
  break;         
 case 3:              
  printf("÷ ");              
  result= a / b;              
  break;         
 default:             
  printf("somethingis wrong! ");              
  break;        
 }
  printf("%d = ", b);        
  scanf("%d", &c);      
  if(c == result)        
  {             
   score+= 10;           
   printf("Right ");        
  }        
  else        
  {             
   printf("Wrong ");      
  }
 }
   printf("Yourscore is: %d ", score);  
   return 1;
}