Seg fault: C++ Quicksort using vectors and iterators

I am trying to implement quicksort using C++ containers and iterators.

I am new to C++ STL.

I am getting a seg fault. For all my C programs I always used valgrind to figure out situations like this but right now its not helping. Any tips/suggestions/solutions will be appreciated.

#include <iostream>
#include <fstream>
#include <vector>
#include <iterator>
#include <algorithm>

using namespace std;

void print(vector<int> A){
    for(vector<int>::iterator i = A.begin(); i != A.end(); i++)
        cout << *i << " ";
    cout<<endl;
}

vector<int>::iterator Partition(vector<int>::iterator l, vector<int>::iterator r){
    int x = *l;
    vector<int>::iterator i = l + 1;
    for(vector<int>::iterator j = l + 1; j <= r; j++){
        if(*j < x){
            iter_swap(j, i);
            i++;
        }
    }
    iter_swap(l, (i - 1));
    return i - 1;
}

void QuickSort(vector<int>::iterator l, vector<int>::iterator r){
    if (distance(l, r) <= 1) return;
    vector<int>::iterator p = Partition(l, r);
    QuickSort(l, p - 1);
    QuickSort(l + distance(l, p), r);
}

int main(int argc, const char * argv[]){
    if (argc != 2){
        cout << "Usage: ./Sort <file_name>" << endl; //<file_name> refers to a file of integers where each line contains a number
        return EXIT_FAILURE;
    }

    ifstream infile(argv[1]);

    vector<int> A;
    int num;
    while(infile >> num){
        A.push_back(num);
    }
    //print(numbers);
    int n = 0;
    print(A);
    QuickSort(A.begin(), A.end());
    print(A);
    //cout << n << endl;
    return EXIT_SUCCESS;
}