Submission #362254

#	Time	Username	Problem	Language	Result	Execution time	Memory
362254		SeDunion	XOR Sum (info1cup17_xorsum)	C++17	45 / 100	1678 ms	8172 KiB

xorsum

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e6 + 66;
//
// bit
// 2^bit
// a[i] %= 2^(bit+1)
// 1 <= a[i] <= 2^(bit+1)-1
// 2 <= a[i] + a[j] <= 2^(bit+2)-2
// 0010000000
// 0011111111
// 0110000000
// 0111111111
//
// 2^bit <= a[i] + a[j] <= 2^(bit+1)-1
// 2^(bit+1)+2^(bit) <= a[i] + a[j] <= 2^(bit+2)-1

const int LOG = 30;

int a[N], b[N];

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	int n;
	cin >> n;
	for (int i = 1 ; i <= n ; ++ i) cin >> a[i];
	int ans = 0;
	for (int bit = 0 ; bit < LOG ; ++ bit) {
		int parity = 0;
		for (int i = 1 ; i <= n ; ++ i) {
			b[i] = a[i] % (1 << (bit+1));
		}
		sort(b+1,b+1+n);
		//for (int i = 1 ; i <= n ; ++ i) cout << b[i] << " \n"[i == n];
		for (int i = 1, l = n, r = n ; i <= n ; ++ i) {
			while (l >= 1 && (1<<bit) <= b[i] + b[l]) --l;
			while (r >= 1 && b[i] + b[r] > (1<<(bit+1))-1) --r;
			int cur = max(r,i) - max(l,i-1);
			if (r < i) break;
			if (cur & 1) parity ^= 1;
			//cout << i << " " << l + 1 << " " << r << "\n";
		}
		for (int i = 1, l = n, r = n ; i <= n ; ++ i) {
			while (l >= 1 && (1<<(bit+1))+(1<<bit) <= b[i] + b[l]) --l;
			while (r >= 1 && b[i] + b[r] > (1ll<<(bit+2))-1) --r;
			int cur = max(r,i) - max(l,i-1);
			if (r < i) break;
			if (cur & 1) parity ^= 1;
			//cout << i << " " << l + 1 << " " << r << "\n";
		}
		ans += parity * (1 << bit);
	}
	cout << ans;
}

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