Submission #357681

#	Time	Username	Problem	Language	Result	Execution time	Memory
357681		Mlxa	XOR Sum (info1cup17_xorsum)	C++14	100 / 100	755 ms	31212 KiB

xorsum

#ifdef LC
#include "pch.h"
#else
#include <bits/stdc++.h>
#endif
using namespace std;
using ll = long long;
#define int ll
#define all(x) x.begin(), x.end()
#define x first
#define y second
#define mp make_pair
#define mt make_tuple

/*
bit = 0
oth = 1 && carry = 0
OR
oth = 0 && carry = 1

bit = 1
oth = 0 && carry = 0
OR
oth = 1 && carry = 1
*/

int solve(int a[], int an, int b[], int bn, int msk, bool carry) {
	int answer = 0;
	int j = 0;
	for (int i = an; i--; ) {
		while (j < bn && (a[i] & msk) + (b[j] & msk) <= msk) {
			++j;
		}
		if (!carry) {
			answer += j;
		} else {
			answer += bn - j;
		}
	}
	return answer;
}

const int N = 1e6 + 10;

int n;
int a[N];
int bs[2];
int b[2][N];

signed main() {
#ifdef LC
	assert(freopen("input.txt", "r", stdin));
#endif
	ios::sync_with_stdio(0); cin.tie(0);

	cin >> n;
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	int answer = 0;
	for (int l = 0; l < 30; ++l) {
		// cout << "l = " << l << endl;
		// for (int i = 0; i < n; ++i) {
		// 	cout << ((a[i] >> l) & 1) << " " << (a[i] & ((1 << l) - 1)) << endl;
		// }
		// cout << "---" << endl;
		int msk = (1 << l) - 1;
		bs[0] = bs[1] = 0;
		for (int i = 0; i < n; ++i) {
			int bit = (a[i] >> l) & 1;
			b[bit][bs[bit]++] = a[i];
		}
		copy_n(b[0], bs[0], a);
		copy_n(b[1], bs[1], a + bs[0]);
		int ones = 0;
		for (int i = 0; i < n; ++i) {
			if (((a[i] + a[i]) >> l) & 1) {
				++ones;
			}
		}
		ones += solve(b[0], bs[0], b[0], bs[0], msk, true);
		ones += solve(b[0], bs[0], b[1], bs[1], msk, false);
		ones += solve(b[1], bs[1], b[0], bs[0], msk, false);
		ones += solve(b[1], bs[1], b[1], bs[1], msk, true);
		assert(ones % 2 == 0);
		ones /= 2;
		if (ones % 2) {
			answer ^= 1 << l;
		}
	}
	cout << answer << endl;
	return 0;
}

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