Submission #1148327

#	Time	Username	Problem	Language	Result	Execution time	Memory
1148327		weakweakweak	XOR Sum (info1cup17_xorsum)	C++20	100 / 100	682 ms	30244 KiB

xorsum

#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
using pii = pair<int,int>;
#define fs first 
#define sc second

int n, a[1888888], B = 30;
vector<pii> v;

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);
    cin >> n;
    // if (n > 100000) B = 12;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    int ans = 0;
    for (int b = 0; b < B; b++) {
        int z = (1<<(b+1))-1;
        if (b > 0) {
            vector<pii> v2[2];
            for (int i = 0; i < n; i++) v2[(a[v[i].sc]>>b)&1].emplace_back(z&a[v[i].sc], v[i].sc); 
            v.clear();
            for (auto x : v2[0]) v.push_back(x);
            for (auto x : v2[1]) v.push_back(x);
        }
        else {
            for (int i = 1; i <= n; i++) v.emplace_back(z&a[i], i);
            sort(v.begin(), v.end());
        }
        // for (auto x : v) cout << x.fs << ' ';
        // cout << '\n';

        long long cnt = 0;
        int th1 = (1<<b), th2 = (1<<(b+1)), th3 = th1+th2;
        for (int i = 0, j=n, j2=n, j3=n; i < n; i++) {
            while (j3 > 0 and v[i].fs+v[j3-1].fs >= th3) j3--;
            if (j2 > j3) j2 = j3;
            while (j2 > 0 and v[i].fs+v[j2-1].fs >= th2) j2--;
            if (j > j2) j = j2;
            while (j > 0  and v[i].fs+v[j-1].fs  >= th1) j--;
            int a1 = n - j, a2 = n - j2, a3 = n - j3;
            cnt += (a1-a2);
            cnt += (a3);
        }
        for (int i = 1; i <= n; i++) if ((a[i]+a[i])&(1<<b)) cnt++;
        cnt /= 2;
        if (cnt & 1) ans += (1<<b);
    }
    cout << ans << '\n';
}

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