#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <iterator>
using namespace std;
 
template<typename Cont>
Cont diff(Cont const &a, Cont const &b) {
    using T = typename Cont::value_type;
    set<T> sa(begin(a), end(a)),
           sb(begin(b), end(b));
 
    Cont result;
    set_symmetric_difference(
        begin(sa), end(sa),
        begin(sb), end(sb),
        back_inserter(result));
    return result;
}
 
int main() {
	vector<int> a {1, 2, 3, 4, 5},
                b {1, 3, 6, 7, 4};
 
    for(int el: diff(a, b)) {
        cout << el << " ";
    }
	return 0;
}

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