单链表

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

typedef struct node
{
        int  num;
        struct node* next;
}node;

node *head = NULL;

node *make_node(int data)
{
        node *p = (node *)malloc(sizeof(node));

        if(p == NULL)
        {
                return NULL;
        }
        else
        {
                p -> num = data;
                p -> next = NULL;
        }
        return p;
}

void insert_node_head(node *p)
{
        p -> next = head;
        head = p;
}

void insert_node_tail(node *p)
{
        node *p1 = head;
        node *end = NULL;
        if(head == NULL)
        {
                head = p;
        }
        else
        {
                while(p1 -> next  != NULL)
                {
                        p1 = p1 -> next;
                }
                p1 -> next = p;
                p1 = p;
                p -> next = NULL;
        }
}

void free_node(node *p)
{
        free(p);
}

void traverse()
{
        node *p = head;
        if( p == NULL)
        {
                printf("no num/n");
        }
        while(p != NULL)
        {
                printf("%d  ",p -> num);
                p = p -> next;
        }
        printf("\n");
}

node *find(int n)
{
        node *p = head;
        while(p != NULL)
        {
                if(n == p -> num)
                {
                        return p;
                }
                p = p -> next;
        }
        return NULL;
}


void rm_node(node *p)
{
        if(p == head)
        {
                head = head  -> next;
                p -> next = NULL;
                return;
        }
        else
        {
                node *pre = head;
                while(pre != NULL)
                {
                        if(pre -> next == p)
                        {
                                pre -> next = p -> next ;
                                p -> next = NULL;
                                return ;
                        }
                        pre = pre -> next;
                }
        }
}

void destory()
{
        node *p = head ;
        while(head != NULL)
        {
                head = head -> next;
                free_node(p);
                p = head;
        }
}
int main()
{
        node *p = make_node(1);
        insert_node_tail(p);

        p = make_node(3);
             insert_node_tail(p);

        p = make_node(5);
         insert_node_tail(p);

        p = make_node(7);
         insert_node_tail(p);

        traverse();

        int  a = 3;
        p = find(3);
        if(p == NULL)
        {
                printf("can not find num3\n");
        }
        else
        {
                printf("%d\n",p -> num);
        }
        destory();
        traverse();
}