1747D - Yet Another Problem - CodeForces Solution

#include <bits/stdc++.h>
#define endl "\n"
using namespace std;
typedef long long LL;
const LL N = 2e5 + 10, INF = 0x3f3f3f3f, mod = 1e9 + 7;
LL a[N], s[N], sum[N];

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);

    // LL t;
    // cin >> t;
    // while (t--)
    // {
        LL n, k;
        cin >> n >> k;
        map<int, set<int>> mp[2];
        for (LL i = 1; i <= n; i++)
        {
            cin >> a[i];
            s[i] = (s[i - 1] ^ a[i]);
            sum[i] = sum[i - 1] + a[i];
            if (i & 1)  mp[1][s[i]].insert(i);
            else    mp[0][s[i]].insert(i);
        }

        for (LL i = 1; i <= k; i++)
        {
            LL l, r;
            cin >> l >> r;
            LL res = (s[r] ^ s[l - 1]);
            if (res != 0)
            {
                cout << -1;
            }
            else
            {
                if (r - l + 1 == 2)   
                {
                    if (a[l] || a[r])   cout << -1;
                    else    cout << 0;
                }
                else
                {
                    if (sum[r] - sum[l - 1] == 0)   cout << 0;
                    else
                    {
                        // cout << "*";
                        if ((r - l + 1) & 1)    cout << 1;
                        else
                        {
                            if (!a[l] || !a[r]) cout << 1;
                            else
                            {
                                int k = (l & 1);
                                if (mp[k].count(s[l - 1]))
                                {
                                    auto pos = mp[k][s[l - 1]].upper_bound(l);
                                    // cout << pos - mp[k].begin() << " ";
                                    if (pos == mp[k][s[l - 1]].end())   cout << -1;
                                    else if (*pos < r)   cout << 2;
                                    else    cout << -1;
                                }
                                else    cout << -1;
                            }
                        }
                    }
                }
            }
            cout << endl;
        }
    //     cout << endl;
    // }
    return 0;
}