Submission #883567

#	Time	Username	Problem	Language	Result	Execution time	Memory
883567		pragmatist	XOR Sum (info1cup17_xorsum)	C++17	100 / 100	688 ms	27616 KiB

xorsum

#include<iostream>
#include<cassert>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<vector>
#include<stack>
#include<set>
#include<queue>
#include<map>

using namespace std;

const int N = (int)1e6 + 7;
const int M = (int)1e6 + 7;
const int inf = (int)1e9 + 7;
const int MOD = (int)998244353;
const long long INF = (long long)1e18 + 7; 

int mult(int x, int y) {
	return 1ll*x*y%MOD;
}

int sum(int x, int y) {
	x += y;
	if(x >= MOD) {
		x -= MOD;
	}
	return x;
}

int sub(int x, int y) {
	x -= y;
	if(x < 0) {
		x += MOD;
	}
	return x;
}

int n, a[N], b[N];

long long f(int l, int r) {
	long long cur = 0;
	int j = 0, k = 0;
	for(int i = n; i >= 1; --i) {
	    while(k<n && a[k+1] <= r-a[i]) {
	    	k++;
	    }
	    while(j<n && a[j+1] < l-a[i]) {
	    	j++;
	    }
		cur += min(i, k)-min(i, j);	
	}
	return cur;
}

int main() {	
	ios_base::sync_with_stdio(NULL);
	cin.tie(0);
	cin >> n;
	for(int i = 1; i <= n; ++i) {
		cin >> a[i];
	}
	int ans = 0;
	sort(a+1, a+1+n);
	for(int j = 29; j >= 0; --j) {
		long long cur = f((1 << j), (1 << (j+1))-1) + f((1 << j) + (1 << (j+1)), (1 << (j+2))-1);
		if(cur&1) {
			ans |= (1 << j);
		}
		vector<int> c, d, e(n);
		for(int i = 1; i <= n; ++i) {
			if(a[i] >> j & 1) {
				c.push_back(a[i]^(1<<j));
			} else {
				d.push_back(a[i]);
			}	
		}
		merge(c.begin(), c.end(), d.begin(), d.end(), e.begin());
		assert((int)e.size() == n);
		for(int i = 1; i <= n; ++i) {
			a[i] = e[i-1];
		}
	}
	cout << ans << "\n";
	return 0;
}

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