1. Problem description

        Each employee record contains the employee number （no）、 full name （name）、 Department number （depno） And wages （salary）. Design a program to complete the following functions ：

        Employee record data structure ：

typedef struct
{
		int no;					// Employee number 
		char name[10];		    // full name 
		int depno;			    // Department number 
		float salary;		    // Wages 
} EmpType;
EmpType  employee[10]={
   {1001," Zhang San ",01,2605},{...}};

        Establish employee records based on the above data structure , A single linked list of leading nodes is established accordingly L.

        Single linked table data structure ：

typedef struct node
{
	EmpType data;				// Store employee information 
	struct node *next;			// Pointer to the next node 
}  EmpList;						// Employee single linked list node type 

        Through a single linked list L Realization ：

        （1） Enter an employee record

        （2） Show all employee records

        （3） By number no Sort all employee records incrementally

        （4） By department number depno Sort all employee records incrementally

        （5） By salary salary Sort all employee records incrementally

        （6） Delete the employee record with the specified employee number

        （7） Delete the entire single linked list

2. Outline design

        This procedure has 8 A function ：

        （1）create()： Create a single chain table , Allocate memory for the head node , And its next Domain empty .

        （2）init(EmpList* head)： Initialize linked list , Using head insertion method , add to 10 Employees are recorded in the linked list .

        （3）input(EmpList* head)： Create a new node , Store the employee information entered by the user in the data field , Then insert the node behind the head node , Complete the addition of an employee record .

        （4）show(EmpList* head)： Traverse each data node of the linked list , Print out all employee records .

        （5）sort(EmpList* head,int op)： according to op The value of is used to sort the linked list incrementally according to different standards .op=3 Sort by employee number ,op=4 Sort by department number ,op=5 Sort by salary . If there is only a header node or only one data node , You don't have to sort ; Otherwise, the bubble method is used to sort .

        （6）delete_by_no(EmpList* head)： Receive the employee number entered by the user , Traverse the data nodes of the linked list , Find the node corresponding to the employee number , The of the previous node next The domain points to the next node , Then release the space of the node , Delete the specified employee number record .

        （7）delete_all(EmpList* head)： Traverse the data nodes of the linked list , One by one, release the space of nodes , Complete the deletion of all employee records .

        （8）menu()： Print menu .

3. Program realization

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

//  Employee record structure 
typedef struct
{
    int no;             // Employee number 
    char name[10];      // full name 
    int depno;          // Department number 
    int salary;         // Wages 
} EmpType;

//  Employee single linked list node type 
typedef struct node
{
    EmpType data;       // Store employee information 
    struct node *next;  // Pointer to the next node 
} EmpList;

//  Create a chain header 
EmpList* create()
{
    EmpList* head = (EmpList*)malloc(sizeof(EmpList));
    if (head!=NULL)
    {
        head->next=NULL;
        return head;
    }
    printf(" Out of memory , Failed to create linked list ！\n\n");
    return NULL;
}

//  Initialize linked list 
void init(EmpList* head)
{
    int i;
    EmpList* p = head;
    EmpType emps[10]=
    {
        {1009," waiter ",101,6270},
        {1001," Li Si ",103,2605},
        {1002," Laolu ",102,2500},
        {1006," Zhang San ",102,7500},
        {1004," Dried tangerine or orange peel ",103,6400},
        {1005," Zhao Liu ",101,3200},
        {1007," Xiao Wang ",101,1383},
        {1008," Wang Wu ",103,2328},
        {1003," Morpheme ",104,1800},
        {1010," Cheng ",101,2328}
    };

    //  The first interpolation 
    for (i=0; i<10; i++)
    {
    	//  Apply for memory for the node  
        EmpList* q = (EmpList*)malloc(sizeof(EmpList));
        if (q==NULL)
        {
            printf(" Out of memory , Failed to initialize the linked list ！\n\n");
            return ;
        }
        
        //  Insert the new node behind the head node 
        q->data = emps[i];
        q->next = p->next;
        p->next = q;
    }
}

//  Enter an employee record 
void input(EmpList* head)
{
    EmpType emp;
    printf(" Please enter employee information （ Use space spacing ）:");
    scanf("%d %s %d %d",&emp.no,emp.name,&emp.depno,&emp.salary);
    EmpList* p = (EmpList*)malloc(sizeof(EmpList));
    if (p==NULL)
    {
        printf(" Out of memory , Failed to add record ！\n\n");
        return ;
    }
    p->data = emp;
    p->next = head->next;
    head->next = p;
    printf(" Add success ！\n\n");
}

//  Print menu 
void menu()
{
    printf("-------------------- Employee information system --------------------\n");
    printf("                 1: Add employee record \n");
    printf("                 2: Show all employee records \n");
    printf("                 3: Sort by job number increment \n");
    printf("                 4: Sort by department number \n");
    printf("                 5: Sort by salary increase \n");
    printf("                 6: Delete the record of the specified job number \n");
    printf("                 7: Delete all records \n");
    printf("                 0: Exit the system \n");
    printf("----------------------------------------------------\n\n");
}

//  Show all records 
void show(EmpList* head)
{
    EmpType emp;
    EmpList* p = head->next;
    printf("\n"); 
    printf(" Employee number \t full name \t\t department \t Wages \n");
    while (p!=NULL)
    {
        emp = p->data;
        p=p->next;
        printf("%d\t%-12s\t%d\t%d\n",emp.no,emp.name,emp.depno,emp.salary);
    }
    printf("\n");
}

//  Ascending sort  
void sort(EmpList* head,int op)
{
    EmpList* pre;// The previous node 
    EmpList* cur;// The current node 
    EmpList* nx;// The last node  
    EmpList* end=NULL;// Caudal node 
     
	//  If the linked list has only one header node or only one data node , No sorting  
    if (head->next==NULL || head->next->next==NULL)
    {
        return ;
    }
    
    //  Bubble sort  
    while(head->next!=end)
    {
        pre=head;
        cur=head->next;
        nx=cur->next;
        while(nx!=end)
        {
            switch(op)
            {
            case 3:
            	//  If the value of the current node is greater than the value of the next node , Then exchange them  
                if (cur->data.no>nx->data.no)
                {
                	//  Exchange the nodes they point to  
                    cur->next=nx->next;
                    pre->next=nx;
                    nx->next=cur;
                    EmpList* temp=nx;
                    nx=cur;
                    cur=temp;
                }
                break;
            case 4:
                if (cur->data.depno>nx->data.depno)
                {
                    cur->next=nx->next;
                    pre->next=nx;
                    nx->next=cur;
                    EmpList* temp=nx;
                    nx=cur;
                    cur=temp;
                }
                break;
            case 5:
                if (cur->data.salary>nx->data.salary)
                {
                    cur->next=nx->next;
                    pre->next=nx;
                    nx->next=cur;
                    EmpList* temp=nx;
                    nx=cur;
                    cur=temp;
                }
                break;
            }
            pre=pre->next;
            cur=cur->next;
            nx=nx->next;
        }
        end=cur;
    }
    show(head);
}

// Delete the record of the specified job number 
void delete_by_no(EmpList* head)
{
    EmpList* p=head;
    EmpList* q;
    int no;
    printf(" Please enter the employee number to delete the record ：");
    scanf("%d",&no);
    while(p->next!=NULL)
    {
    	//  Let the of the previous node first next Point to the last node of the deleted node , Then release the space of the deleted node  
        if (p->next->data.no == no)
        {
            q=p->next;
            p->next=q->next;
            free(q);
            printf(" Delete successful ！\n\n");
            return ;
        }
        p=p->next;
    }
    printf(" There is no employee information of this job number ！\n\n"); 
}

//  Delete all records 
void delete_all(EmpList* head)
{
    EmpList* p=head->next;
    EmpList* q;
    while(p!=NULL)
    {
        q=p;
        p=p->next;
        free(q);
    }
    head->next=NULL;
    printf(" Delete all successfully ！\n\n");
}

int main()
{
    int op;
    EmpList* link=create();
    init(link);
    menu();
    do
    {
        printf(" Please select ：");
        scanf("%d",&op);
        switch (op)
        {
        case 1:
            input(link);
            break;
        case 2:
            show(link);
            break;
        case 3:
        case 4:
        case 5:
            sort(link,op);
            break;
        case 6:
            delete_by_no(link);
            break;
        case 7:
            delete_all(link);
            break;
        case 0:
            exit(1);
        default:
            printf(" Input error , Please re-enter ！\n\n");
            break;
        }
    }
    while(op!=-1);
    return 0;
}

4. Implementation interface