功能如下
1. 添加学生
2. 删除学生
3. 修改学生信息
4. 获得学生信息
5. 获得所有学生信息

B树创建优势

1. 查找非常快
   2.任何一个学生只需要查询几步（譬如2的32次方的学生，每次只需要32次遍历）
   B树缺点
   1.严重浪费空间，有点符合动态规划的：以空间换时间

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct stu{
    char name[20];
}stu;
typedef struct Node{
    struct Node *pre,*L,*R;
    int id;
    struct stu *info;
}biTree;

biTree* init(){
    biTree *root=(biTree*)malloc(sizeof(biTree));
    root->pre=NULL;
    root->L=NULL;
    root->R=NULL;
    return root;
}

void binary(int x,int b[]){
    int i,j=0,temp,count=0;
    memset(b,0,32*sizeof(int));
    if(x==0){
        b[0]=0;
    }
    while(x!=0){
        b[count]=x%2;
        x/=2;
        count++;    
    }
    i=31;
    while(j<=i){
        temp=b[i];b[i]=b[j];b[j]=temp;
        i--;j++;
    }
}

void creat(biTree *root,int id){
    biTree *bt,*pre;
    int b[32];
    bt=root;
    binary(id,b);
    for (int i = 0; i < 32; ++i){
        if(b[i]==0){
            if(bt->L!=NULL){
                bt=bt->L;
            }else{
                pre=bt;         
                bt=(biTree*)malloc(sizeof(biTree));
                pre->L=bt;
                bt->pre=pre;
                bt->L=NULL;
                bt->R=NULL;
            }
        }else if(b[i]==1){
            if(bt->R!=NULL){
                bt=bt->R;
            }else{
                pre=bt;
                bt=(biTree*)malloc(sizeof(biTree));
                pre->R=bt;
                bt->pre=pre;
                bt->L=NULL;
                bt->R=NULL;
            }
        }
    }
    bt->id=id;
    bt->info=(stu*)malloc(sizeof(stu));
    printf("\n\t\t\tplease input the name:");
    scanf("%s",bt->info->name);
}

biTree* getnode(biTree *root,int id){
    int b[32];
    biTree *bt=root;
    binary(id,b);
    if(bt==NULL){
        return NULL;
    }
    for (int i = 0; i < 32; ++i){
        if(bt==NULL){
            return NULL;
        }
        if(b[i]==0){
            bt=bt->L;
            if(bt==NULL){
                return NULL;
            }
        }else if(b[i]==1){
            bt=bt->R;
            if(bt==NULL){
                return NULL;
            }
        }
    }
    return bt;
}

int main(){
    biTree *root;
    biTree *stu,*pre; 
    int code,studentId,i,b[32]; 
    int a[1000];
    char name[20];
    memset(a,0,sizeof(a));
    root=init();
    while(1){

        printf("\n\t\t\t==============student system===============");
        printf("\n\t\t\t 1.add student");
        printf("\n\t\t\t 2.del student");       
        printf("\n\t\t\t 3.modify student");
        printf("\n\t\t\t 4.get student information");
        printf("\n\t\t\t 5.get all student information");

        printf("\n\t\t\tplease input the choice:");
        scanf("%d",&code);
        switch(code){
            case 1:
                printf("\n\t\t\tplease input studentId you want to add:");
                scanf("%d",&studentId);
                if(a[studentId]==0){
                    a[studentId]=1;
                    creat(root,studentId);
                    printf("\n\t\t\tadd success");
                    break;
                }
                else if(a[studentId]==1){
                    printf("\n\t\t\tthe student is already exit!");
                    break;
                }
                break;              
            case 2:
                printf("\n\t\t\tplease input the studentId you want del:");
                scanf("%d",&studentId);
                binary(studentId,b);
                stu=getnode(root,studentId);
                if(stu==NULL){
                    printf("\n\t\t\tthe student don't exit");
                    break;
                }
                pre=stu->pre;
                if(b[31]==0){
                    pre->L=NULL;
                }else{
                    pre->R=NULL;
                }
                free(stu);
                a[studentId]=0;
                printf("\n\t\t\tdel success");
                break;
            case 3:
                printf("\n\t\t\tplease input the studentId you want modify:");
                scanf("%d",&studentId);
                stu=getnode(root,studentId);
                if(stu==NULL){
                    printf("\n\t\t\tthe student don't exit");
                    break;
                }
                printf("\n\t\t\tid: %d,name: %s",stu->id,stu->info->name);
                printf("\n\t\t\tplease input the new name:");
                scanf("%s",stu->info->name);
                printf("\n\t\t\tmodify success!");
                break;
            case 4:
                printf("\n\t\t\tplease input the studentId you want search:");
                scanf("%d",&studentId);
                stu=getnode(root,studentId);
                if(stu==NULL){
                    printf("\n\t\t\tthe student don't exit!");
                    break;
                }
                printf("\n\t\t\tid: %d,name: %s",stu->id,stu->info->name);
                break;
            case 5:
            for(int i=0;i<1000;i++){
                if(a[i]!=0){
                    stu=getnode(root,i);
                    printf("\n\t\t\tid: %d ,name: %s",stu->id,stu->info->name);
                }
            }
            break;
        }
    }
    return 0;
}