#include <stdio.h>
#include <stdlib.h>
#include<string.h>
struct Student{
        int ID;
        int class;
        char name[10];
        float score[3];
        float sum;
        }stu[3];
int id1;  //标记删除的学生学号

void print(void)
        {
            printf("1.input\n");
            printf("2.delete\n");
            printf("3.select\n");
            printf("4.order\n");
            printf("5.output\n");
            printf("6.quit\n");
            printf("please input your option\n");
        }

void input(struct Student stu[],int j)  //用来输入数据的函数，当用户输入1时，执行此函数。
    {
        char ch[10],ch1[10]={"yes"},ch2[10]={"no"};
        printf("id ");
        scanf("%d",&stu[j].ID);
        printf("class ");
        scanf("%d",&stu[j].class);
        printf("name ");
        scanf("%s",stu[j].name);
        printf("score1 ");
        scanf("%f",&stu[j].score[0]);
        printf("score2 ");
        scanf("%f",&stu[j].score[1]);
        printf("score3 ");
        scanf("%f",&stu[j].score[2]);
        stu[j].sum=stu[j].score[0]+stu[j].score[1]+stu[j].score[2];

        printf("continue?");
        scanf("%s",ch);
        if(strcmp(ch,ch1)==0)
        {
            j++;
            input(stu,j);
        }
        if(strcmp(ch,ch2)==0)
         print();
   }

int delete(struct Student stu[])  //当用户输入数字2时，操作此函数，进行学生数据的删除
    {
        char ch1[10]={"yes"},ch2[10]={"no"},ch3[10];
        int i,j;
        scanf("%d",&id1);
        for(i=0;i<3;i++)
        {
           if(id1!=stu[i].ID)
           {
               printf("%d,%d,%s,",stu[i].ID,stu[i].class,stu[i].name);
               for(j=0;j<3;j++)
               {printf("%.1f,",stu[i].score[j]); }
               printf("%.1f\n",stu[i].sum);
           }
        }
         printf("continue?");
         scanf("%s",ch3);
         return id1;
         if(strcmp(ch3,ch1)==0) delete(stu);
        if(strcmp(ch3,ch2)==0) print();
   }

void select(struct Student stu[])    //当用户输入数字3时，运行这个函数
    {
        char ch[10],ch1[10]={"yes"},ch2[10]={"no"},ch3[10];
        int id,cla,i,j,flag=0;
        scanf("%d",&id);
        for(i=0;i<3;i++)
        {
           if(id==stu[i].ID)
           {
               printf("%d,%d,%s,",stu[i].ID,stu[i].class,stu[i].name);
               for(j=0;j<3;j++)
                   {printf("%.1f,",stu[i].score[j]);}
               printf("%.1f\n",stu[i].sum);
               flag++;
           }
        }
        if(flag==0) printf("there is no eligible student");
        printf("continue?");
        scanf("%s",ch);
        if(strcmp(ch,ch1)==0)
       {
            scanf("%d",&cla);
             for(i=0;i<3;i++)
              {
                if(cla==stu[i].class)
                  {
                     printf("%d,%d,%s,",stu[i].ID,stu[i].class,stu[i].name);
                       for(j=0;j<3;j++)
                        {printf("%.1f,",stu[i].score[j]);}
                     printf("%.1f\n",stu[i].sum);
                  }
             }
       }
       printf("continue?");
       scanf("%s",ch3);
       if(strcmp(ch3,ch2)==0) print();
 }

void order(struct Student stu[])   //当用户输入4时，进行此函数，进行排序
    {
        int i,j;
        struct Student temp;
       for(i=0;i<2;i++)
            for(j=0;j<2-i;j++)
               {
                    if(stu[i].ID!=id1)
                      {
                        if(stu[j].class>stu[j+1].class)
                            {temp=stu[j];stu[j]=stu[j+1];stu[j+1]=temp;}
                        if(stu[j].class==stu[j+1].class)
                            {
                               if(stu[j].sum>stu[j+1].sum)
                                  {temp=stu[j];stu[j]=stu[j+1];stu[j+1]=temp;}
                            }
                      }
               }
        for(i=0;i<3;i++)
               {
                   if(stu[i].ID!=id1)
                      {
                          printf("%d,%d,%s,",stu[i].ID,stu[i].class,stu[i].name);
                          for(j=0;j<3;j++)
                              {printf("%.1f,",stu[i].score[j]);}
                          printf("%.1f\n",stu[i].sum);
                      }
              }
             print();
}

void output(struct Student stu[])  //当用户输入5时，进行数据的输出。
      {
         int i,j;
        for(i=0;i<3;i++)
           {
                if(stu[i].ID!=id1)
                   {
                      printf("%d,%d,%s,",stu[i].ID,stu[i].class,stu[i].name);
                       for(j=0;j<3;j++)
                          {printf("%.1f,",stu[i].score[j]);}
                      printf("%.1f\n",stu[i].sum);
                   }
          }
        print();
      }

void match(int n)  //将用户输入的数字与函数进行搭配
    {
        switch(n)
          {
              case 1:input(stu,0); break;
              case 2:delete(stu);break;
              case 3:select(stu);break;
              case 4:order(stu);break;
              case 5:output(stu);break;
              case 6:break;
          }
    }

int main()
        {
            int a[6];         //用数组存储这输入的数字，并进行搭配。
            print();
            scanf("%d",&a[0]);
            if(a[0]!=6)
             { match(a[0]);
               scanf("%d",&a[1]);
                 if(a[1]!=6)
                      {match(a[1]);
                       scanf("%d",&a[2]);
                       if(a[2]!=6)
                           {match(a[2]);
                              scanf("%d",&a[3]);
                                if(a[3]!=6)
                                   {match(a[3]);
                                     scanf("%d",&a[4]);
                                       if(a[4]!=6)
                                          {match(a[4]);
                                            scanf("%d",&a[5]);
                                             if(a[5]!=6)
                                             {match(a[5]);}
                                          }
                                   }
                             }

                         }
             }
            return 0;
      }

换了后对了，可是为什么呢？？？

谢谢