【数据结构与算法】基本数据结构——队列的链式表示

该队列为链式队列，初建队列时，队头和队尾均指向头结点，头结点中不存放
数据，只存放指针，头结点的下一个节点才开始存放数据，这这样做的目的是
为了在入队和出队时方便对队列的操作，而不用考虑特殊情况。

C语言源代码

#include<stdio.h>#include<stdlib.h>typedef struct Node{int data;struct Node *pNext;}NODE,*PNODE;typedef struct Queue{PNODE front;  //队头指针PNODE rear;   //队尾指针}QUEUE,*PQUEUE;PQUEUE create_queue();bool is_empty(PQUEUE);void en_queue(PQUEUE, int);bool de_queue(PQUEUE,int *);void destroy_queue(PQUEUE);void traverse_queue(PQUEUE);int main(){int data_de = 0;         //用来保存出队的元素值//创建队列并进行入队测试PQUEUE pS = create_queue();en_queue(pS,2);en_queue(pS,4);en_queue(pS,6);traverse_queue(pS);//出队测试if(de_queue(pS,&data_de))printf("delete succeed,the deleted data is: %d\n",data_de);elseprintf("queue is empty! delete falied!\n");traverse_queue(pS);//销毁队列测试destroy_queue(pS);printf("queue destroyed!\n");traverse_queue(pS);return 0;}/*创建一个空队列，队头指针和队尾指针都指向头结点，头结点中不存放数据，只存放指针*/PQUEUE create_queue(){PQUEUE pS = (PQUEUE)malloc(sizeof(Queue));pS->front = (PNODE)malloc(sizeof(NODE));if(!pS || !pS->front){printf("pS or front malloc failed!!");exit(-1);}else{pS->rear = pS->front;pS->front->pNext = NULL;}return pS;}/*判断队列是否为空*/bool is_empty(PQUEUE pS){if(pS->front == pS->rear)return true;elsereturn false;}/*进队函数，从队尾进队，队头指针保持不变*/void en_queue(PQUEUE pS, int e){PNODE pNew = (PNODE)malloc(sizeof(NODE));if(!pNew){printf("pNew malloc failed");exit(-1);}else{pNew->data = e;pNew->pNext = NULL;pS->rear->pNext = pNew;pS->rear = pNew;}return;}/*出队函数，从队头出队，队尾指针保持不变，但当最后一个元素出队时，需要对队尾指针重新赋值，使其指向头结点*/bool de_queue(PQUEUE pS,int *pData){if(is_empty(pS))return false;else{PNODE p = pS->front->pNext;*pData = p->data;pS->front->pNext = p->pNext;//这里是队列头元素出队的特殊情况，一般情况下，删除队头元素时//仅需修改头结点中的指针，但当队列中最后一个元素被删除时，//队列尾指针也丢失了，因此需对队尾指针重新赋值（指向头结点）。if(pS->rear == p)         pS->rear = pS->front;free(p);}return true;}/*遍历队列，从对头向队尾依次输出队中的元素*/void traverse_queue(PQUEUE pS){if(is_empty(pS))printf("there is no data in the queue!\n");else{PNODE pCurrent = pS->front->pNext; printf("Now datas int the queue are:\n");while(pCurrent){printf("%d ",pCurrent->data);pCurrent = pCurrent->pNext;}printf("\n");}return;}/*销毁队列,头结点也被销毁,最后也将pS节点销毁，并将其指向为空，避免垂直指针的产生*/void destroy_queue(PQUEUE pS){if(is_empty(pS))return;else{while(pS->front){pS->rear = pS->front->pNext;free(pS->front);pS->front = pS->rear;}}free(pS);pS = 0;return;}