Submission #389331

#	Time	Username	Problem	Language	Result	Execution time	Memory
389331		wiwiho	XOR Sum (info1cup17_xorsum)	C++14	11 / 100	92 ms	460 KiB

xorsum

#include <bits/stdc++.h>

#define mp make_pair
#define F first
#define S second
#define eb emplace_back
#define printv(a, b) { \
    for(auto pv : a) b << pv << " "; \
    b << "\n"; \
}

using namespace std;

typedef long long ll;

using pii = pair<int, int>;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;

    vector<ll> cnt(4001);
    int ans = 0;
    for(int i = 1; i <= n; i++){
        int v;
        cin >> v;
        cnt[v]++;
    }

    for(int i = 1; i <= 4000; i++){
        for(int j  = 1; j < i; j++){
            if(cnt[i] * cnt[j] % 2) ans ^= i + j;
            //cerr << cnt[i] << " " << cnt[j] << " " << cnt[i] * cnt[j] << " " << i + j << " " << ans << "\n";
        }
        if(cnt[i] * (cnt[i] + 1) / 2 % 2) ans ^= i + i;
    }
    cout << ans << "\n";

    return 0;
}

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