NAME

std::priority_queue::top - std::priority_queue::top

Synopsis

const_reference top() const;

Returns reference to the top element in the priority queue. This element will be
removed on a call to pop(). If default comparison function is used, the returned
element is also the greatest among the elements in the queue.

Parameters

(none)

Return value

Reference to the top element as if obtained by a call to c.front()

Complexity

Constant.

Example

// Run this code

#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' }