數據結構複習第二章:隊列

鏈表實現隊列

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

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

node *head = NULL;

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

     if(p == NULL)
    {
        printf("malloc fair");
        exit(1);
    }

    p->data = data;

    return p;
}

int head_insert(node *p)//頭插法
{
    p->next = head;
    head = p;
}

int traverse()
{
    node *pre = head;
    while(pre != NULL)//指針指向的當前節點不爲空
    {
        printf("%d ",pre->data);

        pre = pre->next;
    }

    printf("\n-----------------\n");
}

node *find_item(int data)
{
    node *pre = head;
    while(pre != NULL)//指針指向的當前節點不爲空
    {
        if(pre->data == data)
        {
            return pre;
        }

        pre = pre->next;
    }

    return NULL;
}

int delete_node(node *p)
{
    if(head == p)
    {
        head = head->next;
        return 1;
    }


    node *pre = head;

    while(pre->next != NULL)//刪除時要看下一個節點節點是否存在 刪除的方法所決定
    {
        if(pre->next = p)
        {
            pre->next = p->next;//刪除節點  
            free_node(p);
            return ;
        }

        pre = pre->next;
    }

    return NULL;
}

int destroy()
{
    node *pre = head;
    node *p = NULL;

    while(pre != NULL)
    {
        p = pre->next;
        free_node(pre);
        pre = p;
    }

    return ;
}

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


int is_empty()
{
    if(head == NULL)
    {
        return 1;
    }else
    {
        return 0;
    }
}

int enqueue(int data)//入隊 
{
    node *p = mk_node(data);
    if(head == NULL)//隊列爲空 直接放
    {
        p->next = head;
        head = p;

        return ;
    }

    node *tail = head;//設置一個尾節點
    while(tail->next != NULL)//末尾沒有節點了
    {
        tail = tail->next; //找到最後一個爲空的結點
    }

    p->next = tail->next;//插在尾指針之前
    tail->next = p;
}


int dequeue()//出隊 打印出當前指針所指向的數據 釋放節點
{
    node *pre = head;
    head = head->next;
    int data = pre->data;
    free_node(pre);

    return data ;
}


int main()
{
    enqueue(1);
    enqueue(2);
    enqueue(3);
    enqueue(4);

    traverse();

    while(!is_empty())
    {
        printf("dequeue(): %d \n",dequeue());
    }

    printf("\n");

    return 0;
}