Submission #440901

#	Time	Username	Problem	Language	Result	Execution time	Memory
440901		zxcvbnm	XOR Sum (info1cup17_xorsum)	C++14	45 / 100	1683 ms	8200 KiB

xorsum

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int L = 29;
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    vector<int> a(n);
    for(int i = 0; i < n; i++) {
        cin >> a[i];
    }
    vector<int> p = {1};
    for(int i = 1; i <= L+1; i++) {
        p.push_back(p[i-1]*2);
    }

    vector<int> cnt(L+1, 0);

    for(int j = L; j >= 0; j--) {
        vector<int> x(n);
//        cout << j << " " << p[j] << "\n";
        for(int i = 0; i < n; i++) {
            x[i] = (a[i] % p[j+1]);
        }
        sort(x.begin(), x.end());

        for(int i = 0; i < n; i++) {
            int pos1, pos2, pos3;
            pos1 = lower_bound(x.begin(), x.end(), p[j]-x[i]) - x.begin();
            pos2 = lower_bound(x.begin(), x.end(), 2*p[j]-x[i]) - x.begin();
            pos3 = lower_bound(x.begin(), x.end(), 3*p[j]-x[i]) - x.begin();
            assert(pos1 <= pos2 && pos2 <= pos3);
            int curr = (pos2 - pos1) + (n - pos3);
            if ((x[i] + x[i]) & p[j]) curr++;
//            cout << j << " " << i << " " << pos1 << " " << pos2 << " " << pos3 << "\n";

            cnt[j] += curr;
        }
    }

    ll ans = 0;
    for(int i = 0; i <= L; i++) {
        cnt[i] /= 2;
//        cout << cnt[i] << "\n";
        if (cnt[i] % 2) {
            ans += p[i];
        }
    }
    cout << ans << "\n";
    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 38 / 38
• Subtask 5: 0 / 23