Problem: 2049C - MEX Cycle
Language: C++20 (GCC 13-64)

Previous submission (verdict: Runtime error on test 2):
#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>



using namespace std;

using namespace __gnu_pbds;



#define endl "\n"

#define ll long long

#define IOS ios_base::sync_with_stdio(false); cin.tie(nullptr);



const int N = 2e5 + 5;



int ans[N];





int main() {

    IOS;

    int t;

    cin >> t;

    while (t--) {

        int n, x, y;

        cin >> n >> x >> y;

        x--, y--;

        if (x > y) {

            swap(x, y);

        }

        for (int i = 0; i < n; i++) {

            ans[i] = -1;

        }

        if (y - x == 1 || (x == 0 && y == n - 1)) {

            ans[0] = 0;

        } else {

            ans[x] = 0;

            ans[y] = 1;

            int xa = (x + 1) % n, xb = (x - 1 + n) % n;

            int ya = (y + 1) % n, yb = (y - 1 + n) % n;

            ans[xa] = 1;

            ans[xb] = 1;

            ans[ya] = 0;

            ans[yb] = 0;

            if (xa == ya || xa == yb) {

                ans[xa] = 2;

            }

            if (xb == ya || xb == yb) {

                ans[xb] = 2;

            }

        }

        int i = y;

        while (i != x) {

            if (ans[i] == -1) {

                set<int> st;

                if (ans[(i - 1 + n) % n] != -1) {

                    st.insert(ans[(i - 1 + n) % n]);

                }

                if (ans[(i + 1) % n] != -1) {

                    st.insert(ans[(i + 1) % n]);

                }

                if (*st.begin() == 1) {

                    ans[i] = 0;

                } else if (*st.rbegin() == 0 || st.size() == 1) {

                    ans[i] = 1;

                } else {

                    ans[i] = 2;

                }

            }

            i = (i + 1) % n;

        }

        i = x;

        while (i != y) {

            if (ans[i] == -1) {

                set<int> st;

                if (ans[(i - 1 + n) % n] != -1) {

                    st.insert(ans[(i - 1 + n) % n]);

                }

                if (ans[(i + 1) % n] != -1) {

                    st.insert(ans[(i + 1) % n]);

                }

                if (*st.begin() == 1) {

                    ans[i] = 0;

                } else if (*st.rbegin() == 0 || st.size() == 1) {

                    ans[i] = 1;

                } else {

                    ans[i] = 2;

                }

            }

            i++;

        }

        for (int i = 0; i < n; i++) {

            cout << ans[i] << " ";

        }

        cout << endl;

    }

    return 0;

}



Submission (verdict: Runtime error on test 3):
#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>



using namespace std;

using namespace __gnu_pbds;



#define endl "\n"

#define ll long long

#define IOS ios_base::sync_with_stdio(false); cin.tie(nullptr);



const int N = 2e5 + 5;



int ans[N];





int main() {

    IOS;

    int t;

    cin >> t;

    while (t--) {

        int n, x, y;

        cin >> n >> x >> y;

        x--, y--;

        if (x > y) {

            swap(x, y);

        }

        for (int i = 0; i < n; i++) {

            ans[i] = -1;

        }

        int i;

        if (y - x == 1 || (x == 0 && y == n - 1)) {

            ans[0] = 0;

            i = 1;

            x = 0;

        } else {

            ans[x] = 0;

            ans[y] = 1;

            int xa = (x + 1) % n, xb = (x - 1 + n) % n;

            int ya = (y + 1) % n, yb = (y - 1 + n) % n;

            ans[xa] = 1;

            ans[xb] = 1;

            ans[ya] = 0;

            ans[yb] = 0;

            if (xa == ya || xa == yb) {

                ans[xa] = 2;

            }

            if (xb == ya || xb == yb) {

                ans[xb] = 2;

            }

        }

        while (i != x) {

            if (ans[i] == -1) {

                set<int> st;

                if (ans[(i - 1 + n) % n] != -1) {

                    st.insert(ans[(i - 1 + n) % n]);

                }

                if (ans[(i + 1) % n] != -1) {

                    st.insert(ans[(i + 1) % n]);

                }

                if (*st.begin() == 1) {

                    ans[i] = 0;

                } else if (*st.rbegin() == 0 || st.size() == 1) {

                    ans[i] = 1;

                } else {

                    ans[i] = 2;

                }

            }

            i = (i + 1) % n;

        }

        i = x;

        while (i != y) {

            if (ans[i] == -1) {

                set<int> st;

                if (ans[(i - 1 + n) % n] != -1) {

                    st.insert(ans[(i - 1 + n) % n]);

                }

                if (ans[(i + 1) % n] != -1) {

                    st.insert(ans[(i + 1) % n]);

                }

                if (*st.begin() == 1) {

                    ans[i] = 0;

                } else if (*st.rbegin() == 0 || st.size() == 1) {

                    ans[i] = 1;

                } else {

                    ans[i] = 2;

                }

            }

            i++;

        }

        for (int i = 0; i < n; i++) {

            cout << ans[i] << " ";

        }

        cout << endl;

    }

    return 0;

}