3SUM

#include <bits/stdc++.h>
using namespace std;

set<int> aas;
vector<int> aa;
map<int, pair<int, int>> mm;
map<int, int> qq;

int main() {
	int n, x;
	cin >> n >> x;
	for (int i=0; i<n; i++) {
		int a;
		cin >> a;
		aas.insert(a);
		aa.push_back(a);
		qq[a] = i;
		for (int c : aa) {
			mm[(c+a)] = make_pair(c, a);
		}
	}
	for (auto [a, p] : mm) {
		if (aas.count(x-a)) {
			cout << qq[mm[a].first]+1 << " " << qq[mm[a].second]+1 << " " << qq[x-a]+1 << endl;
			return 0;
		}
	}
	
	cout << "IMPOSSIBLE" << endl;
	return 0;
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: WRONG ANSWER

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: TIME LIMIT EXCEEDED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: TIME LIMIT EXCEEDED

Test 17

Verdict: TIME LIMIT EXCEEDED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: TIME LIMIT EXCEEDED

Test 21

Verdict: TIME LIMIT EXCEEDED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: WRONG ANSWER