Submission #1158158

#	Time	Username	Problem	Language	Result	Execution time	Memory
1158158		itaykarny	XOR Sum (info1cup17_xorsum)	C++20	45 / 100	1694 ms	25676 KiB

xorsum

#include<iostream>
#include<vector>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<string>
#include<math.h>



using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using pll = pair<ll, ll>;
using vpll = vector<pair<ll, ll>>;
using vvpll = vector<vpll>;


void solve() {
	ll n;
	cin >> n;
	ll arr[(ll)1e6 + 1];
	for (ll i = 0; i < n; i++) cin >> arr[i];
	ll ans = 0;
	for (ll b = 0; b < 30; b++) {
		// Look at the first b bits
		vll cur0; // Keep all the numbers that have 0 in the b bit with only their first b-1 bits
		vll cur1; // Keep all the numbers that have 1 in the b bit with only their first b-1 bits
		ll A = ((ll)1 << (b)) - 1;
		for (ll i= 0;i <n; i++) {
			if ((arr[i] >> b) & (ll)1) cur1.push_back(arr[i] & A);
			else cur0.push_back(arr[i] & A);
		}
		sort(cur0.begin(), cur0.end());
		sort(cur1.begin(), cur1.end());
		long long res = 0;
		ll carry = (ll)1 << b;
		for (ll i = 0; i < n; i++) {
			ll curVal = arr[i] & A; // The first b-1 bits of arr[i]
			long long num0 = 0, num1 = 0;
			if (((2 * arr[i]) >> b) & (ll)1) res++;
			if (((arr[i] >> b) & (ll)1) == 0) {
				// The b bit is 0
				// num0 =  The number of numbers that have 0 in the b bit and give carry
				// num1 = The number of numbers that have 1 in the b bit and don't give carry
				num0 = cur0.end() - lower_bound(cur0.begin(), cur0.end(), carry - curVal);
				num1 = lower_bound(cur1.begin(), cur1.end(), carry - curVal) - cur1.begin();
			}
			else {
				// The b bit is 1
				// num0 = The number of numbers that have 0 in the b bit and don't give carry
				// num1 = The number of numbers that have 1 in the b bit and give carry
				num0 = lower_bound(cur0.begin(), cur0.end(), carry - curVal) - cur0.begin();
				num1 = cur1.end() - lower_bound(cur1.begin(), cur1.end(), carry - curVal);
			}
			res += (num0 + num1);
		}
		res /= 2;
		ans += (res % 2) * carry;
	}
	cout << ans << endl;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	solve();
}

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