#include<stdio.h>
#include<string.h>
#define n 4
struct drug
{
    char name[20];
    float price;
    int quantity;
};
struct update  
{
    char na[20];
    float p_increase;
    int    q_increase;
};


void main()
{
    int i,j;
    float sum;
    struct drug items[4]={{"a",39,40},{"b",38,99},{"c",12,400},{"d",31,120}};
    struct update up;
    char ch;
    do
    {
     printf("please input the item you want update\n");
     scanf("%s %f %d",up.na,&up.p_increase,&up.q_increase);

     for(i=0;i<n;i++)
     {
   
        if(strcmp(up.na,items[i].name)==0)

        {
            printf("the %s is to be updated\n",up.na);
            if(up.q_increase+items[i].quantity<0)
                printf("sorry!\n");
            else
                items[i].quantity=items[i].quantity+up.q_increase;
                items[i].price=items[i].price+up.p_increase;
                sum=items[i].price*items[i].quantity;
                printf("%s %f %d %f\n",items[i].name,items[i].price,items[i].quantity,sum);
        }
     else if(strcmp(up.na,items[1].name)&&strcmp(up.na,items[2].name)&&strcmp(up.na,items[3].name)&&strcmp(up.na,items[0].name))

            printf("no the item,sorry!\n");
     }
     printf("any one else?y or no\n");
     scanf("%c",&ch);
   
    }while(ch=='y'||ch=='Y');
   
}
               


这个程序怎么不能循环啊  



我准备输入Y 再循环一次  但是直接显示press any key to continue 为什么啊？？谢谢
还有我这程序红色部分 我想优化下 怎么办？

你换成要求输入0和1选择

ffush(stdin);                          //清除缓冲区
 printf("any one else?y or no\n");

     scanf("%c",&ch);
   
    }while(ch=='y'||ch=='Y');
   
}
        

#include<stdio.h>
#include<string.h>
#define n 4
struct drug
{
    char name[20];
    float price;
    int quantity;
};
struct update  
{
    char na[20];
    float p_increase;
    int    q_increase;
};


void main()
{
    int i,j;
    float sum;
    struct drug items[4]={{"a",39,40},{"b",38,99},{"c",12,400},{"d",31,120}};
    struct update up;
    char ch;
    do
    {
     printf("please input the item you want update\n");
     scanf("%s %f %d",up.na,&up.p_increase,&up.q_increase);

     for(i=0;i<n;i++)
     {
   
        if(strcmp(up.na,items[i].name)==0)

        {
            printf("the %s is to be updated\n",up.na);
            if(up.q_increase+items[i].quantity<0)
                printf("sorry!\n");
            else
                items[i].quantity=items[i].quantity+up.q_increase;
                items[i].price=items[i].price+up.p_increase;
                sum=items[i].price*items[i].quantity;
                printf("%s %f %d %f\n",items[i].name,items[i].price,items[i].quantity,sum);
        }
     else if(strcmp(up.na,items[1].name)&&strcmp(up.na,items[2].name)&&strcmp(up.na,items[3].name)&&strcmp(up.na,items[0].name))

            printf("no the item,sorry!\n");
     }
     fflush(stdin);
     printf("any one else?y or no\n");
     scanf("%c",&ch);
   
    }while(ch=='y'||ch=='Y');
    printf("thanks!bye!\n");
   
}
运行如下

怎么我输入没有的书目  我只想它显示一条no the item,sorry!
结果他显示四条  为什么？

你一个for循环要四次的，
  else if(strcmp(up.na,items[1].name)&&strcmp(up.na,items[2].name)&&strcmp(up.na,items[3].name)&&strcmp(up.na,items[0].name))

            printf("no the item,sorry!\n");     break；    //加个break，没找到，跳出循环。