Submission #62240

#	Time	Username	Problem	Language	Result	Execution time	Memory
62240		Benq	XOR Sum (info1cup17_xorsum)	C++11	45 / 100	1665 ms	13352 KiB

xorsum

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 100001;

int N, x, ans;
vi A, v;

int get(int ind) {
    int cur = 0;
    while (ind < 0) cur -= 2*x, ind += sz(v);
    while (ind >= sz(v)) cur += 2*x, ind -= sz(v);
    return v[ind]+cur;
}

ll tri() {
    ll tot = 0;
    F0R(i,N) if ((2*A[i])&x) tot ++;
    // cout << x << " " << tot << "\n";
    v.clear();
    F0R(i,N) v.pb(A[i]%(2*x));
    sort(all(v));
    
    /*if (x == 16) {
        for (int i: v) cout << i << " ";
        cout << "\n";
    }*/
    
    int i1 = -sz(v), i2 = -sz(v); // first one >= x-i, first one >= 2*x-i
    F0Rd(i,sz(v)) {
        while (get(i1) < x-v[i]) i1 ++;
        while (get(i2) < 2*x-v[i]) i2 ++;
        tot += i2-i1;
        // if (x == 16) cout << i << " " << x-i << " " << 2*x-i << " " << i1 << " " << get(i1) << " " << i2 << " " << get(i2) << "\n";
    }
    return tot/2;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> N; A.resize(N);
    F0R(i,N) cin >> A[i];
    F0R(i,30) {
        x = 1<<i;
        if (tri()&1) ans ^= x;
    }
    cout << ans;
}

/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

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