I am wondering why priority_queue and vector work the totally different way. Here is the sample:
priority_queue<int, vector<int>, less<int> > pq;
pq.push(1);
pq.push(2);
pq.push(3);
// if we print the elem in pq by pop(), we get 3, 2, 1
vector<int> v;
v.push_back(1);
v.push_back(3);
v.push_back(2);
std::sort(v.begin(), v.end(), less<int>());
// but we get 1, 2, 3 for vector
Both priority_queue and vector used less, but why the result is different?
std::less is the default compartor for priority_queue, and std::vector is the default Container, so your code can be simplified as:
priority_queue<int> pq;
According to the doc, it's expected to get the largest value via pop
A priority queue is a container adaptor that provides constant time lookup of the largest (by default) element, at the expense of logarithmic insertion and extraction.
Actually, we get a max heap with std::less as a comparator, this doesn't seem very intuitive. To get a min heap, we need to use std::greater as a comparator.