链队列..

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

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

typedef struct Queue {
  Node head, *tail;
  int length;
}Queue;

Node* getNewNode(int val) {
  Node* p = (Node*)malloc(sizeof(Node));
  p->data = val;
  p->next = NULL;
  return p;
}

Queue* init_queue() {
  Queue* q = (Queue*)malloc(sizeof(Queue));
  q->head.next = NULL;
  q->tail = &q->head;
  q->length = 0;
  return q;
}

void clear_node(Node* node) {
  if (node == NULL) return;
  free(node);
  return;
}

void clear(Queue* q) {
  if (q == NULL) return;
  Node* p = q->head.next, * temp;
  while (p != NULL) {
    temp = p->next;
    clear_node(p);
    p = temp;
  }
  free(q);
  return;
}

int empty(Queue* q) {
  return q->length == 0;
}
int push(Queue* q, int val) {
  if (q == NULL) return 0;
  Node *temp = getNewNode(val);
  q->tail->next = temp;
  q->tail = temp;
  q->length += 1;
  return 1;
 }

int pop(Queue* q) {
  if (q == NULL)return 0;
  if (empty(q)) return 0;
  Node* temp = q->head.next;
  q->head.next = temp->next;
  clear_node(temp);
  q->length -= 1;
  if (q->length == 0) q->tail = &q->head;
  return 1;
}

int front(Queue* q) {
  if (q->head.next == NULL) return 0;
  return q->head.next->data;
}

void output(Queue* q) {
  if (q == NULL) return;
  printf("Queue(%d):[", q->length);
  for (Node* p = q->head.next; p != NULL; p = p->next) {
    p != q->head.next && printf(",");
    printf("%d", p->data);
  }
  printf("]\n");
  return q;
}
int main() {
  srand(time(0));
  Queue* q = init_queue();
  #define MAX_OP 20
  for (int i = 0; i < MAX_OP; i++) {
    int op = rand() % 4;
    int val = rand()%100;
    switch (op) {
      case 0:
      case 1:
      case 2: {
        printf("push %d to the Queue = %d\n", val, push(q, val));
      }break;
      case 3: {
        if (!empty(q)) {
          printf("pop %d from the Queue = ", front(q));
          printf("%d\n",pop(q));
        }
      }break;
    }
    output(q), printf("\n");
  }
  #undef MAX_OP
  clear(q);
  return 0;
}