my-solutions/codeforces/round-923/task-d/main.cpp

#include <iostream>

using namespace std;

const int UNKN = -1;
const int NF = -2;

int main() {
    int t;
    cin >> t;

    for (int y = 0; y < t; y++) {
        int len;
        cin >> len;
        int* arr = new int[len];
        int* cache = new int[len];
        for (int i = 0; i < len; i++) {
            cin >> arr[i];
            cache[i] = UNKN;
        }

        int q_num;
        cin >> q_num;

        for (int v = 0; v < q_num; v++) {
            int l, r;
            cin >> l >> r;
            l--;
            r--;

            if (cache[l] == NF) {
                // Every number will be the same.
                cout << "-1 -1" << endl;
            } else if (cache[l] != UNKN) {
                // Cache hit.
                if (cache[l] > r) {
                    // Another number is beyond our range;
                    cout << "-1 -1" << endl;
                } else {
                    // Answer was cached
                    cout << l + 1 << " " << cache[l] + 1 << endl;
                }
            } else {
                bool found = false;
                
                for (int i = l + 1; i <= r; i++) {
                    if (arr[i] != arr[l]) {
                        // Different number was found
                        cout << l+1 << " " << i+1 << endl;
                        found = true;
                        cache[l] = i;
                        break;
                    }

                    if (cache[i] != UNKN) {
                        // CACHE HIT
                        if (cache[i] > r || cache[i] == NF) {
                            // Not found
                            break;
                        } else {
                            // Answer was cached
                            cout << l + 1 << " " << cache[i] + 1 << endl;
                            found = true;
                            cache[l] = cache[i];
                            break;
                        }
                    }
                }

                if (!found) {
                    // Nothing was found
                    cout << "-1 -1" << endl;
                    if (r == len - 1) {
                        // If we reached the end of our array and nothing was found,
                        // remember this.
                        cache[l] = NF;
                    }
                }
            }
        }

        delete[] cache;
        delete[] arr;
    }
}