Submission #1111131

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111131		RockyB	XOR Sum (info1cup17_xorsum)	C++17	7 / 100	1660 ms	15048 KiB

xorsum

#include <bits/stdc++.h>

using namespace std; 

const int N = 1e6 + 7;

int n;
int a[N];
int main() {
    #ifdef wws
        freopen ("in.txt", "r", stdin);
    #endif

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    int ans = 0;
    for (int b = 0; b < 30; b++) {
        vector<int> v;
        int m = (1 << (b + 1));
        for (int i = 0; i < n; i++) {
            v.push_back(a[i] % m);
            // cout << v.back() << ' ';
        }
        // cout << endl;
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i; j < n; j++) {
                if ((v[i] + v[j]) % m >= m / 2) {
                    ++cnt;
                }
            }
        }
        // cout << cnt << endl;
        if (cnt & 1) {
            ans += (1 << b);
        }
    }

    cout << ans;
}
/*  
    m = 2^ (x+ 1)
    bits: [0...b]

    0 ... 2^b - 1

    m - 1 >= vi + vj >= m / 2
    

*/

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