#include<stdio.h> #include<stdlib.h> #include<time.h> main() { int choice; int a,b,c; srand((unsigned) time(NULL)); printf(" -------------每天一练-------------"); printf(" 1.加法运算:"); printf(" 2.减法运算:"); printf(" 3.乘法运算:"); printf(" 4.除法运算:"); printf(" 5.退出练习:"); while(1) { printf(" 请选择所需要的练习:"); scanf("%d",&choice); switch(choice) { case 1: a=rand()%99; b=99-a; printf(" %d+%d=?",a,b); break; case 2: a=rand()%99; b=99-a; printf(" %d-%d=?",a,b); break; case 3: a=rand()%10; b=50-a; printf(" %d*%d=?",a,b); break; case 4: a=rand()%50; b=100-a; printf(" %d/%d=?",a,b); break; case 5: printf(" 欢迎使用每课一练!!"); exit(0); break; default: printf("输入错误,请重新输入(1-5):"); } } }