inplace_merge

#include <algorithm>
#include <iostream>
#include <vector>
                                                                                                                
using std::vector,
    std::inplace_merge,
    std::sort,
    std::advance,
    std::for_each,
    std::cerr;
                                        
class Temp{
    public:
        int a, b;
        Temp(int i, int j):a(i), b(j){}
};

bool operator<(const Temp& l, const Temp& r)
{
    if((l.a + l.b) < (r.a + r.b)){
        return true;
    }
    return false;
}
                       
typedef vector<Temp> my_vector;
            
int main(){
    my_vector a = {Temp(16, 256), Temp(4, 16), Temp(12, 144), Temp(4, 16), Temp(19, 361), Temp(9, 81), Temp(3, 9), Temp(15, 225), Temp(5, 25), Temp(6, 36), Temp(1, 1), Temp(8, 64), Temp(13, 169), Temp(0, 0), Temp(2, 4), Temp(2, 4), Temp(3, 9), Temp(10, 100), Temp(18, 324), Temp(14, 196), Temp(17, 289), Temp(7, 49), Temp(11, 121)};
     
    auto print = [] (Temp t){
        cerr << "Temp(" << t.a << ", " << t.b << ")\n";
    }; 
    
    auto test = [] (Temp a, Temp b)->bool{
        if(a.a < b.a && a.b < b.b){
            return true;
        }
        return false;
    };
    
    sort(a.begin(), a.end(), test);
    
    my_vector::iterator middle = a.begin();
    
    advance(middle, a.size()/2);
    
    inplace_merge(a.begin(), middle, a.end());
    for_each(a.begin(), a.end(), print);
    
    inplace_merge(a.begin(), middle, a.end(), test);
    for_each(a.begin(), a.end(), print);
    return 0;
}