c – 优先级队列错误的顺序

概述我正在编写霍夫曼编码.这是我的计划的开始： using namespace std;//Counting methodsint *CountCharOccurence(string text){ int *charOccurrence = new int[127]; for(int i = 0; i < text.length(); i++) { c 我正在编写霍夫曼编码.这是我的计划的开始：

using namespace std;//Counting methodsint *CountCharOccurence(string text){    int *charOccurrence = new int[127];    for(int i = 0; i < text.length(); i++)    {        charOccurrence[text[i]]++;    }    return charOccurrence;}voID displayCharOccurence(int *charOccurrence){    for(int i = 0; i < 127; i++)    {        if(charOccurrence[i] > 0)        {            cout << (char)i << ": " << charOccurrence[i] << endl;        }    }}//Node structstruct Node{    public:        char character;        int occurrence;        Node(char c,int occ) {            character = c;            occurrence = occ;        }        bool operator < (const Node* node)        {            return (occurrence < node->occurrence);        }};voID CreateHuffmanTree(int *charOccurrence){    priority_queue<Node*,vector<Node*> > pq;    for(int i = 0; i < 127; i++)    {        if(charOccurrence[i])        {            Node* node = new Node((char)i,charOccurrence[i]);            pq.push(node);        }    }    //Test    while(!pq.empty())    {        cout << "peek: " << pq.top()->character <<  pq.top()->occurrence << endl;        pq.pop();    }}int main(int argc,char** argv) {    int *occurrenceArray;    occurrenceArray = CountCharOccurence("SUSIE SAYS IT IS EASY");    displayCharOccurence(occurrenceArray);    CreateHuffmanTree(occurrenceArray);    return (EXIT_SUCCESS);}

程序首先输出带有出现次数的字符.看起来很好：

 : 4A: 2E: 2I: 3S: 6T: 1U: 1Y: 2

但是必须以优先级顺序显示节点内容的测试循环输出：

peek: Y2peek: U1peek: S6peek: T1peek: I3peek: E2peek:  4peek: A2

这不是预期的顺序.为什么？

解决方法 优先级队列中的元素是指针.由于您没有提供带有2个指向Node对象的函数,因此默认比较函数会比较2个指针.

bool compareNodes(Node* val1,Node* val2){   return val1->occurence < val2->occurence;}priority_queue<Node*,vector<Node*>,compareNodes > pq;

您的 *** 作符< Node与Node *比较时使用

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