Citire rapida si sortare de pair-uri

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>
using namespace std;

typedef pair<int, int> pereche;
vector< pereche > v;

/// Ordine crescatoare dupa primul camp si
/// descrescatoare dupa al II-lea camp
bool comparator( pereche A, pereche B )
{
    if( A.first == B.first )
        return A.second > B.second;
    return A.first < B.first;
}

void afiseaza()
{
    for( int i = 0; i < v.size(); ++i )
        cout << "(" << v[i].first << ", " << v[i].second << ")  ";
    cout << endl << endl;
}


int citeste_rapid_pozitiv()
{
    int s = 0;
    char lit;
    while( (lit = getchar()) && lit >= '0' && lit <='9' )
        {
            s = ( s << 1 ) + ( s << 3 ) + (lit-'0');
        }
    return s;
}

int main()
{
    int n, i, a, b;

    ios::sync_with_stdio( false );
    cin.tie();

    n = citeste_rapid_pozitiv();
    cout << "Am citit rapid: " << n << endl;

    for( i = 0; i < n; ++i )
        {
            a = citeste_rapid_pozitiv();
            b = citeste_rapid_pozitiv();

            //pereche ceva;
            //ceva = make_pair( a, b );
            //v.push_back( ceva );

            v.push_back( make_pair(a, b) );
        }

    afiseaza();
    sort( v.begin(), v.end(), comparator );
    afiseaza();

    return 0;
}