3SUM

#include <iostream>
#include <vector>
#include <string>
using namespace std;
#define long long ll
#define fastio                        \
    ios_base::sync_with_stdio(false); \
    cin.tie(NULL);                    \
    cout.tie(NULL);
// g++ -std=c++17 -o a a.cpp
int main()
{
    fastio;
    int n, x;
    cin >> n >> x;
    vector<int> a(n);
    for (int i = 0; i < n; ++i)
    {
        cin >> a[i];
    }

    bool done = false;
    string res = "";
    for (int i = 0; i < n - 2 && !done; ++i)
    {
        for (int j = i + 1; j < n - 1 && !done; ++j)
        {
            for (int k = j + 1; k < n; ++k)
            {
                if (a[i] + a[j] + a[k] == x)
                {
                    res = to_string(i + 1) + " " + to_string(j + 1) + " " + to_string(k + 1);
                    done = true;
                    break;
                }
            }
        }
    }

    if (!done)
    {
        cout << "IMPOSSIBLE\n";
    }
    else
    {
        cout << res << "\n";
    }

    return 0;
}

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: TIME LIMIT EXCEEDED

Test 11

Verdict: TIME LIMIT EXCEEDED

Test 12

Verdict: TIME LIMIT EXCEEDED

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: TIME LIMIT EXCEEDED

Test 19

Verdict: TIME LIMIT EXCEEDED

Test 20

Verdict: TIME LIMIT EXCEEDED

Test 21

Verdict: TIME LIMIT EXCEEDED

Test 22

Verdict: TIME LIMIT EXCEEDED

Test 23

Verdict: ACCEPTED