Pairs with given sum, C++ (gcc)

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//Title of this code

#include <algorithm>
#include <iostream>
#include <set>
#include <vector>

using namespace std;

// O(n^2)
void pairs_with_given_sum(const vector<int>& t, int sum) {
    
    set<string> s;
    
    for (int i = 0; i < t.size() - 1; ++i)
        for (int j = i + 1; j < t.size(); ++j)
            if (t[i] + t[j] == sum) {
                //ut << t[i] << " - " << t[j] << endl;

s.insert(to_string(t[i]) + " " + to_string(t[j]));
            }

for (auto it = s.begin(); it != s.end(); ++it)
        cout << *it << endl;
  
}

// O(nlog(n) + n)
void pairs_with_given_sum2(vector<int>& t, int sum) {

sort(t.begin(), t.end());
    
    /*
    for (auto it=t.begin(); it!=t.end(); ++it)
        cout << *it << " ";
    cout << endl;
    */
    
    int i = 0;
    int j = t.size() - 1;
    
    int latest = 0;
    
    while (i < j) {
     
        int num = t[i] + t[j];
        
        if (num > sum)
            --j;
        else if (num < sum)
            ++i;
        else {
            if (latest != t[j])
                cout << t[i] << " " << t[j] << endl;
            latest = t[j];
            ++i;
        }
    }

}

int main()
{
    vector<int> t;
    
    t.push_back(4);
    t.push_back(1);
    t.push_back(2);   
    t.push_back(3);
    t.push_back(2);
    t.push_back(5);
    t.push_back(3);
    t.push_back(0);
    t.push_back(3);

pairs_with_given_sum(t, 5);
    cout << endl;
    pairs_with_given_sum2(t, 5);

}

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Compilation time: 1.2 sec, absolute running time: 0.17 sec, cpu time: 0 sec, memory peak: 3 Mb, absolute service time: 1.39 sec