R – Fastest way to find second (third…) highest/lowest value in vector or column

One possible route is to use the index.return argument to sort. I'm not sure if this is fastest though.

set.seed(21)
x <- rnorm(10)
ind <- 2
sapply(sort(x, index.return=TRUE), `[`, length(x)-ind+1)
#        x       ix 
# 1.746222 3.000000

Using C++11/C++0x compile flags, you can

auto it = max_element(std::begin(cloud), std::end(cloud)); // C++11

Otherwise, write your own:

template <typename T, size_t N> const T* mybegin(const T (&a)[N]) { return a; }
template <typename T, size_t N> const T* myend  (const T (&a)[N]) { return a+N; }

See it live at http://ideone.com/aDkhW:

#include <iostream>
#include <algorithm>

template <typename T, size_t N> const T* mybegin(const T (&a)[N]) { return a; }
template <typename T, size_t N> const T* myend  (const T (&a)[N]) { return a+N; }

int main()
{
    const int cloud[] = { 1,2,3,4,-7,999,5,6 };

    std::cout << *std::max_element(mybegin(cloud), myend(cloud)) << '\n';
    std::cout << *std::min_element(mybegin(cloud), myend(cloud)) << '\n';
}

Oh, and use std::minmax_element(...) if you need both at once :/