//佇列(Queue)(先進先出) – 使用鏈結實作（C語言動態記憶體宣告）

//http://openhome.cc/Gossip/AlgorithmGossip/QueueByLink.htm

#include <stdio.h>

#include <stdlib.h>

struct node {

   
int data;

   
struct node *next;

};

typedef struct node Node;

void createq();

void showfront();

void addq(int);

void delq();

void showqueue();

Node *front, *rear;

int main(void) {

   
int input, select;

   
createq();

   
while(1) {

        printf(“\n\n請輸入選項(-1結束)：“);

        printf(“\n(1)插入值至佇列“);

        printf(“\n(2)顯示佇列前端“);

        printf(“\n(3)刪除前端值“);

        printf(“\n(4)顯示所有內容“);

        printf(“\n\$c>”);

        scanf(“%d”, &select);

        if(select == -1)

            break;

        switch(select) {

            case 1:

                printf(“\n輸入值：“);

                scanf(“%d”,
&input);

                addq(input);

                break;

            case 2:

                showfront();

                break;

            case 3:

                delq();

                break;

            case 4:

                showqueue();

                break;

            default:

                printf(“\n選項錯誤！“);

        }

   
}

   
printf(“\n”);

   
return 0;

}

void createq() {

   
front = rear = (Node*) malloc(sizeof(Node));

   
front->next = rear->next = NULL;

}

void showfront(){

   
if(front->next == NULL)

        printf(“\n佇列為空！“);

   
else

        printf(“\n頂端值：%d”, front->next->data);

}

void addq(int data) {

   
Node *newnode;

   
newnode = (Node*) malloc(sizeof(Node));

   
if(front->next == NULL)

        front->next = newnode;

   
newnode->data = data;

   
newnode->next = NULL;

   
rear->next = newnode;

   
rear = newnode;

}

void delq() {

   
Node* tmpnode;

   
if(front->next == NULL) {

        printf(“\n佇列已空！“);

        return;

   
}

   
tmpnode = front->next;

   
front->next = tmpnode->next;

   
free(tmpnode);

}

void showqueue() {

   
Node* tmpnode;

   
tmpnode = front->next;

   
printf(“\n
佇列內容：“);

   
while(tmpnode != NULL) {

        printf(“%d “,
tmpnode->data);

        tmpnode = tmpnode->next;

   
}

}