3SUM

input/code.cpp: In function 'std::vector<long long int> threeSum(std::vector<std::pair<long long int, long long int> >&, long long int)':
input/code.cpp:32:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     for (int i = 0; i < nums.size(); i++){
      |                     ~~^~~~~~~~~~~~~

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

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define int long long
typedef pair<int, int> pii;
typedef vector<int> vi;

vector<int> twoSum(vector<pair<int, int>>& nums, int index, int target){
    int start = index;
    int end = nums.size()-1;
    while (start < end && nums[start].first + nums[end].first != target){
        if (nums[start].first + nums[end].first < target){
            start++;
        } else {
            end--;
        }
    }
    vector<int> sol;
    if (start < end){
        sol.push_back(nums[start].second);
        sol.push_back(nums[end].second);
    }
    return sol;
}

vector<int> threeSum(vector<pair<int, int>>& nums, int target) {
    sort(nums.begin(), nums.end());
    vector<int> temp;
    for (int i = 0; i < nums.size(); i++){
        if (target-nums[i].first > 0){
            temp = twoSum(nums, i+1, target-nums[i].first);
            if (temp.size() != 0){
                temp.push_back(nums[i].second);
                return temp;
            }
        }
    }
    return temp;
}

signed main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);
	
	int n, x;
	cin >> n >> x;
	vector<pair<int, int>> a(n);
	rep(i, 0, n){
	    cin >> a[i].first;
	    a[i].second = i+1;
	}
	
	vector<int> sol = threeSum(a, x);
	if (sol.size() == 0){
	    cout << "IMPOSSIBLE";
	    return 0;
	}
	
	for (int i : sol){
	    cout << i << " ";
	}

	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: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED