优先队列的实现及其在哈夫曼编码中的应用

一.优先队列的实现

template <class T>class priorityQueue{    public:        priorityQueue();        virtual ~priorityQueue();        void insertQueue(T e);        T pop();        int getNumOfQueue(){ return num; }    protected:        struct node        {            T data;            node *next;        };        node* front;        node* rear;        int num;};template <class T>priorityQueue<T>::priorityQueue(){    num = 0;    front = rear = new node;    rear->next = NULL;}template <class T>priorityQueue<T>::~priorityQueue(){    node* p = front->next;    while(p){        delete front;        front = p;        p = front->next;    }    delete front;}template <class T>void priorityQueue<T>::insertQueue(T e){    num++;    node *p = new node, *temp = front->next, *pre = front;    p->data = e;    while(temp && temp->data < e){           //此处若是结构体注意要重载  '<'。        pre = temp;        temp = temp->next;    }    p->next = temp;    pre->next = p;}template <class T>T priorityQueue<T>::pop(){    num--;    T e = front->next->data;    node* p = front->next;    front->next = p->next;    delete p;    return e;}

二.哈夫曼树的实现：

#include <iostream>#include "priorityQueue.h"#include <algorithm>#include <cstring>using namespace std;const int MAXSIZE = 256;struct HfmNode{    char key;    int priority;    HfmNode *lchild, *rchild;};struct codeNode{    char key;    char code[MAXSIZE];};bool cmp(HfmNode a, HfmNode b){    return a.priority < b.priority;}bool operator < (HfmNode a, HfmNode b){    return a.priority < b.priority;}//建立哈夫曼树HfmNode *buildTree(char *str){    int i;    int priority[MAXSIZE] = {0};    priorityQueue <HfmNode> que;    HfmNode *temp = NULL, *ltemp, *rtemp;    for(i=0; str[i]; i++)        priority[str[i]]++;    for(i=0; i<MAXSIZE; i++)        if(priority[i]){            temp = new HfmNode;            temp->key = i;            temp->priority = priority[i];            temp->lchild = NULL;            temp->rchild = NULL;            que.insertQueue(*temp);        }    while(que.getNumOfQueue() > 1){        temp = new HfmNode;        ltemp = new HfmNode;        rtemp = new HfmNode;        *ltemp = que.pop();        *rtemp = que.pop();        temp->priority = ltemp->priority + rtemp->priority;        temp->lchild = ltemp;        temp->rchild = rtemp;        que.insertQueue(*temp);    }    temp = new HfmNode;    *temp = que.pop();    return temp;}bool operator < (codeNode a, codeNode b){    return a.code < b.code;}//将字符和所对应的编码存放起来void encode(HfmNode *tree, char *code, int i, priorityQueue <codeNode> &table){    if(!tree->lchild && !tree->rchild){        code[i] = '\0';        codeNode* temp = new codeNode;        temp->key = tree->key;        strcpy(temp->code, code);        table.insertQueue(*temp);    }    else{        if(tree->lchild){            code[i] = '0';            encode(tree->lchild, code, i+1, table);        }        if(tree->rchild){            code[i] = '1';            encode(tree->rchild, code, i+1, table);        }    }}//打印字符及其对应编码void printfTable(priorityQueue <codeNode> table){     while(table.getNumOfQueue() != 0){        codeNode temp = table.pop();        cout<<temp.key<<':'<<temp.code<<endl;    }}//根据编码找出所代表的字符void decode(HfmNode* tree, char* str, int i){    if('0' == str[i])        decode(tree->lchild, str, i+1);    if('1' == str[i])        decode(tree->rchild, str, i+1);    if(!str[i])        cout<<tree->key;}int main(){//table 记录了字符及其所对应的编码    priorityQueue <codeNode> table;    char str[MAXSIZE], code[MAXSIZE];    cin>>str;    HfmNode *root = buildTree(str);    encode(root, code, 0, table);    printfTable(table);    cout<<"请输入字符所对应的编码：";    cin>>str;    cout<<"对应的字符为：";    decode(root, str, 0);}