队列的链式存储结构,其实就是线性表的单链表,只不过它只能尾进头出而已,我们把它简称为链队列。为了操作上的方便,我们将队头指针指向链队列的头节点,而队尾指针指向终端节点。空队列时,front和rear都指向头节点。
示例程序:(改变自《大话数据结构》)
C++ Code
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#include<iostream>
using namespace std; typedef int ElemType; typedef struct Node { ElemType data; struct Node *next; } Node, *NodePtr; typedef struct { NodePtr front;/* 队头、队尾指针 */ NodePtr rear; } LinkQueue; /* 构造一个空队列 */ bool InitQueue(LinkQueue *Lp) { cout << "Init Queue ..." << endl; NodePtr p = (NodePtr)malloc(sizeof(Node)); p->next = NULL; Lp->front = Lp->rear = p; return true; } /* 销毁队列,包括头节点 */ bool DestroyQueue(LinkQueue *Lp) { cout << "Destroy Queue ..." << endl; while (Lp->front) { Lp->rear = Lp->front->next; free(Lp->front); Lp->front = Lp->rear; } return true; } /* 清为空队列,保留头节点 */ bool ClearQueue(LinkQueue *Lp) { cout << "Clear Queue ..." << endl; NodePtr p = Lp->front->next; Lp->front->next = NULL; Lp->rear = Lp->front; NodePtr q; while (p) { q = p->next; free(p); p = q; } return true; } bool QueueEmpty(LinkQueue LQ) { return LQ.front == LQ.rear; } int QueueLength(LinkQueue LQ) { int i = 0; if (LQ.front == NULL) return 0; NodePtr p = LQ.front->next; while (p) { ++i; p = p->next; } return i; } bool GetHead(LinkQueue LQ, ElemType *pe) { NodePtr p; if (LQ.front == LQ.rear) return false; p = LQ.front->next; *pe = p->data; cout << "Get Head Item : " << *pe << endl; return true; } /* 插入元素Elem为队列的新的队尾元素 */ bool EnQueue(LinkQueue *Lp, ElemType Elem) { cout << "EnQueue Item " << Elem << endl; NodePtr s = (NodePtr)malloc(sizeof(Node)); s->data = Elem; s->next = NULL; Lp->rear->next = s; Lp->rear = s; return true; } /*删除队列的队头元素,用*pe返回其值 */ bool DeQueue(LinkQueue *Lp, ElemType *pe) { if (Lp->front == Lp->rear) return false; NodePtr p = Lp->front->next; *pe = p->data; cout << "DeQueue Item " << *pe << endl; Lp->front->next = p->next; if (Lp->rear == p)/* 若队头就是队尾,则删除后将rear指向头结点*/ Lp->rear = Lp->front; free(p); return true; } /* 从队头到队尾依次对队列中每个元素输出 */ bool QueueTraverse(LinkQueue LQ) { cout << "Queue Traverse ..." << endl; NodePtr p = LQ.front->next; while (p) { cout << p->data << ' '; p = p->next; } cout << endl; return true; } int main(void) { LinkQueue LQ; InitQueue(&LQ); for (int i = 0; i < 5; i++) EnQueue(&LQ, i); QueueTraverse(LQ); int result; GetHead(LQ, &result); DeQueue(&LQ, &result); QueueTraverse(LQ); if (!QueueEmpty(LQ)) cout << "Queue Length : " << QueueLength(LQ) << endl; /*ClearQueue(&LQ);*/ DestroyQueue(&LQ); cout << "Queue Length : " << QueueLength(LQ) << endl; return 0; } |
总的来说,如果可以确定队列的最大值,建议用循环队列,如果不能预估队列的长度,则用链队列。