prq.cpp

#include <functional>
#include <queue>
#include <vector>
#include <iostream>

bool cmpa(int l, int r){
	return l>r;
}

template<typename T> void print_queue(T& q) {
while(!q.empty()) {
	std::cout << q.top() << " ";
	q.pop();
}
std::cout << '\n';
}

template<typename T> void print_queue_2(T& q) {
while(!q.empty()) {
	std::cout << q.top().size() << " ";
	q.pop();
}
std::cout << '\n';
}

struct CompareVec { 
bool operator()(std::vector<int> left, std::vector<int> right) 
{ 
	return left.size() > right.size(); 
} 
}; 

int main() {
std::priority_queue<int> q;

for(int n : {1,8,5,6,3,4,0,9,7,2})
	q.push(n);

print_queue(q);

std::priority_queue<int, std::vector<int>, std::greater<int> > q2;

std::priority_queue<int, std::vector<int>, decltype(&cmpa)> q5(&cmpa);

// std::priority_queue<int, std::vector<int>, decltype(cmpa)> q6(cmpa);

for(int n : {1,8,5,6,3,4,0,9,7,2}){
	q2.push(n);
	q5.push(n);
	// q6.push(n);	
}

print_queue(q2);
print_queue(q5);
// print_queue(q6);

	// Using lambda to compare elements.
auto cmp = [](std::vector<int> left, std::vector<int> right) { return (left.size()) > (right.size()); };

std::priority_queue<std::vector<int>, std::vector<std::vector<int>>, decltype(cmp)> q3(cmp);

std::priority_queue<std::vector<int>, std::vector<std::vector<int>>, CompareVec> q4;

for(int n : {1,8,5,6,3,4,0,9,7,2}){
	q3.push(std::vector<int>(n));
	q4.push(std::vector<int>(n));
}

print_queue_2(q3);

print_queue_2(q4);
}