Thread: Vector and priority queue

i have a sort of this :

Code:

vector < vector <int > >a(100);

say for eg: a[1] has has a list of elements...
I have defined t priority queue stl to hold vector of elemnts..
But on a single push i need all the elemts of 1..ie a[1] to be stored in the priority queue
something like this

Code:

Q.push(a[1])

i need all the elemts of 1 to be pushed at once...
The above doesnt work...it says

No matching.....bla bla bla

any suggestions

Originally Posted by Sebastiani

>> i have a sort of this :

Well it "sort of" matters what *exactly* you have.

>> The above doesnt work...it says "No matching.....bla bla bla"

That just means that you've passed it the wrong...whatchyamacallit.

>> any suggestions

Sure: Don't ask such vague questions.

I did exactly what i asked..The question was not vague...i gave with an example. and snippet...
My question is not answered

So do you want the vector stored in a[1] to get pushed into the priority queue to or do you want the elements in the vector to get pushed? Your question is very vague and I think you might not realize that you're dealing with a vector of a vector of ints, rather than a single vector. To visualize your:

Code:

vector < vector <int > >a(100);

This means that you have a 2-dimensional matrix of integers. If you want to push the integers themselves you'll need to loop through each vector individually.

Originally Posted by anon

Code:

#include <vector>
#include <queue>

int main()
{
    std::vector<std::vector<int> > v(100);
    std::priority_queue<std::vector<int> > pq;
    pq.push(v[1]);
}

This code made me think. How does priority_queue compare elements?

Code:

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

int main()
{
    std::vector<std::vector<int> > v;
    std::vector<int> temp;
    temp.push_back(3);
    temp.push_back(7);
    temp.push_back(2);
    v.push_back(temp);
    temp.clear();
    temp.push_back(13);
    temp.push_back(17);
    temp.push_back(12);
    v.push_back(temp);
    std::priority_queue<std::vector<int> > pq;
    pq.push(v[0]);
    pq.push(v[1]);
    std::cout << pq.top()[0] << std::endl;
}

prints 13 for me. I was wondering if it just looked at the first element of the vector. What exactly is happening? I see it uses a template function

Code:

class Compare = less<typename Container::value_type>

but what is Container::value_type?

Originally Posted by linuxdude

This code made me think. How does priority_queue compare elements?

Code:

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

int main()
{
    std::vector<std::vector<int> > v;
    std::vector<int> temp;
    temp.push_back(3);
    temp.push_back(7);
    temp.push_back(2);
    v.push_back(temp);
    temp.clear();
    temp.push_back(13);
    temp.push_back(17);
    temp.push_back(12);
    v.push_back(temp);
    std::priority_queue<std::vector<int> > pq;
    pq.push(v[0]);
    pq.push(v[1]);
    std::cout << pq.top()[0] << std::endl;
}

prints 13 for me. I was wondering if it just looked at the first element of the vector. What exactly is happening? I see it uses a template function

Code:

class Compare = less<typename Container::value_type>

but what is Container::value_type?

Container::value_type is pretty clearly std::vector<int>. Operator < is defined for any standard vector, using lexicographical_compare.