Submission #496753

#	Time	Username	Problem	Language	Result	Execution time	Memory
496753		armashka	XOR Sum (info1cup17_xorsum)	C++17	11 / 100	158 ms	15920 KiB

xorsum

#include <bits/stdc++.h>
 
//#pragma comment(linker, "/stack:200000000")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
 
#define fast ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
#define all(v) v.begin(),v.end()
#define pb push_back
#define sz size()
#define ft first
#define sd second
 
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef unsigned long long ull;
 
const int N = 1e6 + 5;
const ll M = 1e8;
const ll inf = 1e18;
const ll mod = 1e9;
const double Pi = acos(-1); 
 
ll binpow(ll x, ll ti) { ll res = 1;while (ti){if(ti & 1)res *= x;x *= x;ti >>= 1; x %= mod; res %= mod;} return res;}
ll binmul(ll x, ll ti) { ll res = 0;while (ti){if(ti & 1)res += x;x += x;ti >>= 1; x %= mod; res %= mod;} return res;}
ll nok(ll a, ll b) { return (a*b)/__gcd(abs(a),abs(b)) * (a*b > 0 ? 1 : -1); }
bool odd(ll n) { return (n % 2 == 1); }
bool even(ll n) { return (n % 2 == 0); }            

ll n, a[N], cnt[N], ans;

const void solve(/*Armashka*/) {
	cin >> n;
	for (int i = 1; i <= n; ++ i) cin >> a[i], ++ cnt[a[i]];
	if (n <= 4e3) {
		for (int i = 1; i <= n; ++ i) {
			for (int j = i; j <= n; ++ j) ans ^= (a[i] + a[j]);
		}
	} else {
		for (int i = 1; i <= 4e3; ++ i) {
			for (int j = i; j <= 4e3; ++ j) {
				ll col = cnt[i] * cnt[j];
				if (i == j) col = cnt[i] + cnt[i] * (cnt[i] - 1) / 2;
				if (odd(col)) ans ^= (i + j);
			}
		}
	}
	cout << ans << "\n";
}
            
signed main() {
    fast;
    //freopen("divide.in", "r", stdin);
    //freopen("divide.out", "w", stdout);
    int tt = 1;
    //cin >> tt;
    while (tt --) {
        solve();
    }
}
 
/*
5 4 4
1 2
3 1
3 4
5 3
4 5 2 3
2 1 3 1
1 3 5
2 3 4 5
2 1 3 1
*/

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