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

GITHUB: https://github.com/jash-git/C_Link_Queue

//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;
    }
}