c++11 sorting list using lambda

You may not use std::sort with sequential containers such as std::list or std::forward_list because they have no random access iterator that is required by the standard algorithm std::sort. By this reason the both containers have their own member functions sort.

In you case the code will look the following way:

#include <iostream>
#include <list>
#include <string>

using namespace std;

int main()
{
    list<pair <string, int>> s = {{"two", 2}, {"one", 1}, {"three", 3}};
    s.sort( []( const pair<string,int> &a, const pair<string,int> &b ) { return a.second > b.second; } );

    for ( const auto &p : s )
    {
        cout << p.first << " " << p.second << endl;
    }
}

Take into account that you need to include header <string> otherwise your program will not be compiled with other compilers.

std::sort requires random access iterators, which std::list does not have. But you can use std::list::sort instead.

s.sort([](const pair<string,int>& a, const pair<string,int>& b)
       {
         return (a.second) > (b.second);
       });

where I have made the parameters of the predicate const references, since there is no need to copy them, and doing so might incur some unnecessary overhead.