Priority Queue STL

The priority queue is one of the queues, but it can dynamically sort the data in the queue in a custom way (priority of the data) every push and pop operation, and the queue dynamically adjusts to the way we expect it to be stored.

For example: Our common operation is to sort the data, priority queue default is the high priority of the data, so we push a bunch of numbers in what order, and eventually in the queue always top out the largest element.

Usage:

Example: Push the element 5,3,2,4,6 to the priority queue and print its output.

1. The standard library uses the < operator of the element type by default to determine the precedence relationship between them.

priority_queue<int> PQ;

The < operator shows the high precedence of the elements in integers. Therefore, the output in Example 1 is: 6 5 4 3 2

2. The smaller the data, the higher the priority

priority_queue<int, vector<int;, greater<int

which
The second parameter is a container type.
The second argument is a comparison function.
Therefore, the output in Example 2 is: 2 3 4 5 6

3. Custom priority, overloaded compare symbol overloads default < symbol

1 structnode2 {3FriendBOOL operator<(node n1, node N2)4     {5         returnN1.priority <n2.priority;6     }7     intPriority ;8     intvalue;9};

At this point, you need to customize a priority for each element.

Note: The overload > number compiles an error because the standard library uses the < operator of the element type by default to determine the precedence relationship between them.
and the < operator of the custom type has no direct contact with the > operator

1#include <iostream>2#include <functional>3#include <queue>4 usingNamespace stdnamespace std;5 structnode6 {7FriendBOOL operator<(node n1, node N2)8     {9         returnN1.priority <n2.priority;Ten     } One     intPriority ; A     intvalue; - }; - intMain () the { -     Const intLen =5; -     inti; -     intA[len] = {3,5,9,6,2}; +     //Example 1 -priority_queue<int>Qi; +      for(i =0; i < Len; i++) A Qi.push (A[i]); at      for(i =0; i < Len; i++) -     { -Cout<<qi.top () <<" "; - Qi.pop (); -     } -cout<<Endl; in     //Example 2 -priority_queue<int, vector<int, greater<int> >Qi2; to      for(i =0; i < Len; i++) + Qi2.push (A[i]); -      for(i =0; i < Len; i++) the     { *Cout<<qi2.top () <<" "; $ Qi2.pop ();Panax Notoginseng     } -cout<<Endl; the     //Example 3 +Priority_queue<node>qn; A node B[len]; theb[0].priority =6; b[0].value =1;  +b[1].priority =9; b[1].value =5;  -b[2].priority =2; b[2].value =3;  $b[3].priority =8; b[3].value =2;  $b[4].priority =1; b[4].value =4;  -  -      for(i =0; i < Len; i++) the Qn.push (B[i]); -cout<<"Priority Level"<<'\ t'<<"value"<<Endl;Wuyi      for(i =0; i < Len; i++) the     { -Cout<<qn.top () .priority<<'\ t'<<qn.top () .value<<Endl; Wu Qn.pop (); -     } About     return 0; $}

Priority Queue STL