Analysis of application Method of C + + priority queue

Summary

This article introduces the priority queue from two aspects, 1. The common functions of the priority queue; 2. Priority Queue Code implementation: Heap sequencing and Huffman tree.

Body

I. List of priority queue functions

• Empty () returns true if the priority queue is null
• Pop () Delete the first element
• P Ush () add an element
• Size () returns the number of elements owned in the priority queue
• Top () returns the element with the highest priority in the priority queue

two. Priority Queue code Use cases

Example 1 #include <iostream> #include <queue> #include <deque> #include <vector> #include <funct    Ional> using namespace std; #if _msc_ver > 1020//If VC + + version is > 4.2 using namespace std; STD C + + LIBS implemented in STD #endif//Using priority_queue with deque//use of function greater sorts the IT  EMS in ascending order typedef deque<int, allocator<int> > Intdqu;    typedef priority_queue<int,intdqu, greater<int> > Intprque; Using priority_queue with vectors//use of function less sorts the items in descending order typedef Vector<char,  allocator<char> > Chvector;    typedef priority_queue<char,chvector,less<char> > Chprque;   void Main (void) {int size_q;   Intprque Q;     Chprque p;   Insert items in the Priority_queue (uses deque) Q.push (42);   Q.push (100);   Q.push (49);     Q.push (201); Output the item at the top using top () cout << q.top () << ENdl   Output the size of priority_queue size_q = Q.size ();   cout << "Size of Q is:" << size_q << Endl;   Output items in Priority_queue using Top ()//and use POPs () to get to next item until//Priority_queue is empty   while (!q.empty ()) {cout << q.top () << Endl;   Q.pop ();   }//Insert items in the priority_queue (uses vector) P.push (' C ');   P.push (' a ');   P.push (' d ');   P.push (' m ');     P.push (' h ');     Output the item at the top using top () cout << p.top () << Endl;   Output the size of priority_queue size_q = P.size ();     cout << "Size of P is:" << size_q << Endl;   Output items in Priority_queue using Top ()//and use POPs () to get to next item until//Priority_queue is empty   while (!p.empty ()) {cout << p.top () << Endl;   P.pop (); }  }

Output: Size of Q is:4 42 49 100 201

m size of p is:5 m h D C a

Example 2#include<iostream>  #include <queue>  using namespace std;  struct CMP  {   bool operator () (const int &a,const int &b)     {   return a<b;//sorted in ascending order     }  };  typedef priority_queue< int, VECTOR<INT>, cmp > qu;  void Main ()  {   Qu P;   P.push (a);   P.push (+);   P.push ();   P.push (201);   while (!p.empty ())   {   cout << p.top () << Endl;   P.pop ();   }  

Output Result: 201  the

Example 3 (Implementation of Huffman tree with Priority_queue): #include <iostream> #include <queue> using namespace std;   Class Node {public:int weight;   Node* left;   node* right;    Node (int w, node* L, node* R): Weight (W), left (L), right (R) {} Node (int w): Weight (W), Left (null), right (null) {}}; Class CMP//functor for Priority_queue class {Public:bool operator () (node* a,node* b) {return a->weight>=b-&gt   ; weight;    }  };   The pointer is passed in, if the object is implemented, you do not know the direction of the left and right pointers//in the sequence traversal void Inorder (node* p) {if (P! = NULL) {inorder (p->left);   cout<<p->weight<< '/t ';   Inorder (P->right);  }} void Freetree (node* p)//Destroy binary tree {if (p->left!=null) Freetree (p->left);  if (p->right!=null) Freetree (p->right);  Delete (p);   } int main () {node* m1,*m2;   Priority_queue<node*,vector<node*>,cmp> Q;   for (int i=0;i<6;++i)//6 nodes {int N=rand ()%100;    Q.push (new Node (n));//The weighted value randomly generates cout<<n<< '/t ';   } cout<<endl; for (iNT J=1;J&LT;6;++J)//merge 5 times {m1=q.top (); Q.pop (); M2=q.top ();   Q.pop ();   int w=m1->weight+m2->weight;   Q.push (New Node (W,M1,M2));   } node* root=q.top ();   Inorder (root);   cout<<endl;     Freetree (root);   System ("pause");  return 0;  }

Output Result: 0 0 235 136

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Analysis of application Method of C + + priority queue