3SUM

input/code.cpp: In function 'int main()':
input/code.cpp:41:34: warning: comparison of integer expressions of different signedness: 'ull' {aka 'long long unsigned int'} and 'll' {aka 'long long int'} [-Wsign-compare]
   41 |             if(h2.count(aa) && j != idx){
      |                                ~~^~~~~~

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;

int main(){
    ull n, x;
    cin >> n >> x;

    vector<ll> as;
    unordered_map<ll, int> h;

    as.reserve(n);

    for(ull i=0; i<n; i++){
        ll a;
        cin >> a;
        as.push_back(a);
    }

    for(ull i=0; i<n; i++){
        h[x - as[i]] = i;
    }

    auto it = h.begin();
    for(ull i=0; i<h.size(); i++, it++){
        // unordered_map<ll, int> h;
        auto target = *it;
        ll t = target.first;
        ll idx = target.second;

        map<ll, int> h2;
        for(ull j=0; j<n; j++){
            // if(j == idx)
            //     continue;
            h2[t - as[j]] = j;
        }

        for(ull j=0; j<n; j++){
            auto aa = as[j];
            if(h2.count(aa) && j != idx){
                cout << (idx+1) << " " << (h2[aa]+1) << " " << (j+1) << endl;
                return 0;
            }
        }

    }
    cout << "IMPOSSIBLE" << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: ACCEPTED

Test 13

Verdict: TIME LIMIT EXCEEDED

Test 14

Verdict: TIME LIMIT EXCEEDED

Test 15

Verdict: TIME LIMIT EXCEEDED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: TIME LIMIT EXCEEDED

Test 22

Verdict: TIME LIMIT EXCEEDED

Test 23

Verdict: WRONG ANSWER