Submission #1319686

#	Time	Username	Problem	Language	Result	Execution time	Memory
1319686		muhammad-ahmad	XOR Sum (info1cup17_xorsum)	C++20	18 / 100	72 ms	8244 KiB

xorsum

// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
#include <numeric>
#include <stack>
#include <chrono>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

void fast_io() {
	// freopen("", "r", stdin);
	// freopen("", "w", stdout);
	ios::sync_with_stdio(0);
	cin.tie();
	cout.tie();
	cout << setprecision(9);
}

#define int long long
#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define fi first
#define se second
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>

const int N = 4e3 + 5;

int C[N] = {};

void solve() {
	int n; cin >> n;
	int a[n + 1];
	for (int i = 1; i <= n; i++) cin >> a[i];
	if (n < N){
		int ans = 0;
	for (int i = 1; i <= n; i++){
		for (int j = i; j <= n; j++){
			// cout << '(' << i << " , " << j << ") : " << i << " + " << j << " = " << i + j << endl;
			int x = a[i]; x += a[j];
			ans = (ans ^ x);
		}
	}	
	cout << ans << endl;
	return;
	}
	int ans = 0;
	for (int i = 1; i <= n; i++) C[a[i]]++;
	for (int i = 1; i <= 2 * N; i++){
		for (int j = 1; j < i; j++){
			int x = j, y = i - j;
			if (x >= N or y >= N) continue;
			if (x > y) break;
			if (x != y){
				int c = C[x] * C[y];
				if (c % 2) ans = (ans ^ i);
			}
			else {
				int c = (C[x] * (C[y] - 1)) / 2 + C[x];
				if (i == 12 && j == 3) cout << c << endl;
				if (c % 2) ans = (ans ^ i);
			}
		}
	}
	cout << ans << endl;
}

signed main() {
	fast_io();
	srand(chrono::steady_clock::now().time_since_epoch().count());
	int tc = 1;
	// cin >> tc;
	while (tc--) solve();
	return 0;
}

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