Pair sort

input/code.cpp: In function 'int main()':
input/code.cpp:47:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |     for(int i=0; i< swaps.size(); i++){
      |                  ~^~~~~~~~~~~~~~

#include <iostream>
#include <vector>

using namespace std;

void swap(vector<int>& vec, int a, int b){
    int i = vec[a];
    vec[a] = vec[b];
    vec[b] = i;

}

int find_pos(const vector<int>& vec, int min, int find){

    for(int i=vec.size(); i>min; i--){
        if(vec[i]==find)return i;
    }
    return -1;
}

int main(){
    int n;
    cin >> n;
    vector<int> vec((2*n));
    for(int i=0; i<2*n; i++) cin >> vec[i];

    vector<pair<int,int>> swaps;

    int num = vec[0];
    for(int i=1; i<2*n; i++){
        if((i%2)==1){
            if(vec[i]!=num){
                int pos = find_pos(vec, i, num);
                swaps.push_back(make_pair(i, pos));
                swap(vec,i,pos);


            }
        }
        else{
            num=vec[i];
        }
    }

    cout << swaps.size() <<endl;

    for(int i=0; i< swaps.size(); i++){
        cout << swaps[i].first+1 << " " <<swaps[i].second+1 <<endl;
    }



}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED