How can we find second maximum from array efficiently?

Question

Is it possible to find the second maximum number from an array of integers by traversing the array only once?

As an example, I have a array of five integers from whi

Answer 1

How about the following below. make_heap is O(n) so this is efficient and this is 1-pass We find the second max by taking advantage that it must be one of the heap children of the parent, which had the maximum.

#include 
#include 

int main()
{
    int arr[6]={0,1,2,3,4,5};

    std::make_heap(arr, arr+6);
    std::cout << "First Max: " << arr[0] << '\n';
    std::cout << "Second Max: " << std::max(arr[1], arr[2]) << '\n';
    return 0;
}