std::priority_queue front
- since C++98
// Const version only
const_reference top() const;
Returns a reference
to the top element in the priority queue.This element will be the first element to be removed on a call to
pop()
.
note
If default comparison function is used, the returned element is also the greatest among the elements in the queue.
note
Effectively calls c.front()
.
Parameters
(none)
Return value
Reference to the top element.
Exceptions
(none)
Complexity
Constant - (1).
Example
main.cpp
#include <queue>
#include <iostream>
struct Event
{
int priority{};
char data{' '};
friend bool operator< (Event const& lhs, Event const& rhs) {
return lhs.priority < rhs.priority;
}
friend std::ostream& operator<< (std::ostream& os, Event const& e) {
return os << "{ " << e.priority << ", '" << e.data << "' } ";
}
};
int main()
{
std::priority_queue<Event> events;
std::cout << "Fill the events queue:\n";
for (auto const e: { Event{6,'L'}, {8,'I'}, {9,'S'}, {1,'T'}, {5,'E'}, {3,'N'} }) {
std::cout << e << ' ';
events.push(e);
}
std::cout << "\n" "Process events:\n";
for (; !events.empty(); events.pop()) {
Event const& e = events.top();
std::cout << e << ' ';
}
}
Output
Fill the events queue:
{ 6, 'L' } { 8, 'I' } { 9, 'S' } { 1, 'T' } { 5, 'E' } { 3, 'N' }
Process events:
{ 9, 'S' } { 8, 'I' } { 6, 'L' } { 5, 'E' } { 3, 'N' } { 1, 'T' }