How to find the index of smallest 3 elements in an array

[Lost User]

How can we find the index of smallest 3 elements in an array. Below code finds the index of largest 3 elements in an array.

#include #include using namespace std;

int main()
{
double arr[] = {0.2, 1.0, 0.01, 3.0, 0.002, -1.0, -20};

priority_queue < pair > pQueue;

for (int i = 0; i < 7; i++)
{
pQueue.push(pair(arr[i], i));
}

int k = 3; // number of indices we need

for (int i = 0; i < k; ++i)
{
int ki = pQueue.top().second;
cout << ki << " ";
pQueue.pop();
}

}

[Jochen Arndt]

See std::priority_queue - cppreference.com[^]:

Quote:

A user-provided Compare can be supplied to change the ordering, e.g. using std::greater would cause the smallest element to appear as the top().

Another solution would be inverting the sign of the items pushed into the queue:

pQueue.push(pair(-arr[i], i));

[Lost User]

Where should I put

std::greater

in the code.

[Jochen Arndt]

See the link from my answer. It contains example code showing that it must be passed as 3rd template parameter. So you have to pass also the 2nd parameter. As with any templates, T (uppercase) is a placeholder for the corresponding type which is std::pair in your case. So it must be (untested):

priority_queue < pair, vector>, greater> > pQueue;

[Lost User]

Thanks it worked