3SUM

input/code.cpp: In function 'int main(int, char**)':
input/code.cpp:17:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |     for (int i=3; i<nums.size(); i++) {
      |                   ~^~~~~~~~~~~~

#include <iostream>
#include <vector>
#include <algorithm>


int main(int argc, char **argv) {
    long long n, x;
    std::cin >> n >> x;

    std::vector<long long> nums(n+1);
    for (int i=1; i<=n; i++) {
        std::cin >> nums[i]; 
    }

    std::sort(nums.begin(), nums.end());
    
    for (int i=3; i<nums.size(); i++) {
        int l = 1;
        int r = i-1;
        while (l < r) {
            long long sum = nums.at(l) + nums.at(r) + nums.at(i);
            if (sum == x) {
                std::cout << l << " " << r << " " << i << std::endl;
                return 0;
            } else if (sum < x) {
                l++;
            } else {
                r--;
            }
        }
    }

    std::cout << "IMPOSSIBLE" << std::endl;

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: WRONG ANSWER

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: ACCEPTED

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED