CODEWITHSUNDEEP
c++priority-queue
Will
Will

Reputation: 113

Is possible to use container's size as priority_queue's priority in C++?

#include <iostream>
#include <queue>

using namespace std;

int main() {
  priority_queue<vector<int>> q;
  q.push({1, 2, 3});
  q.push({3});
  q.push({1, 2});
  q.push({0, 1, 2, 3, 4});

  while (!q.empty()) {
    cout << q.top().size() << endl;
    q.pop();
  }
}

The above code will output

1
3
2
5

I want to get

1
2
3
5

I searched around but not able to figure out the correct way or not sure it's possible. Any help will be great, thanks in advance.

Upvotes: 2

Views: 62

Answers (2)

Ken Y-N
Ken Y-N

Reputation: 15009

Looking at the documentation, something like this might work:

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

Upvotes: 2

Vlad Feinstein
Vlad Feinstein

Reputation: 11311

While constructing priority_queue, you can provide your own compare function.

Please see https://en.cppreference.com/w/cpp/container/priority_queue

// Using lambda to compare elements.
auto cmp = [](int left, int right) { return (left ^ 1) < (right ^ 1); };
std::priority_queue<int, std::vector<int>, decltype(cmp)> q3(cmp);

Just change the types per your requirement

Upvotes: 2

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