Submission #872397

#	Time	Username	Problem	Language	Result	Execution time	Memory
872397		racsosabe	XOR Sum (info1cup17_xorsum)	C++14	45 / 100	202 ms	4524 KiB

xorsum

#include<bits/stdc++.h>
using namespace::std;

const int N = 100000 + 5;

int n;
int a[N];

vector<pair<int, int>> parse(vector<int> &v) {
	int l = 0;
	vector<pair<int, int>> res;
	while(l < v.size()) {
		int r = l;
		while(r < v.size() and v[l] == v[r]) r += 1;
		res.emplace_back(v[l], r - l);
		l = r;
	}
	return res;
}

long long get_crossed(vector<pair<int, int>> a, vector<pair<int, int>> b, int m) {
	int sum_a = 0, sum_b = 0;
	for(auto x : a) sum_a += x.second;
	for(auto x : b) sum_b += x.second;
	long long res = 1ll * sum_a * sum_b;
	int at = b.size() - 1;
	int sum = 0;
	for(auto x : a) {
		if(x.first == 0) continue;
		int want = m - x.first;
		while(at >= 0 and b[at].first >= want) {
			sum += b[at].second;
			at -= 1;
		}
		res -= 1ll * x.second * sum;
	}
	return res;
}

long long get_pairs(vector<pair<int, int>> v, int m) {
	long long res = 0;
	int at = (int)v.size() - 1;
	int sum = 0;
	for(int i = 0; i < v.size(); i++) {
		int want = m - v[i].first;
		while(at > i and v[at].first >= want) {
			sum += v[at].second;
			at -= 1;
		}
		while(at < i) {
			at += 1;
			sum -= v[at].second;
		}
		res += 1ll * v[i].second * sum;
		if((v[i].first << 1) >= m) res += 1ll * v[i].second * (v[i].second - 1) / 2;
	}
	return res;
}

long long get_bits(int b, int p) {
	vector<int> ones;
	vector<int> zeros;
	vector<int> total;
	for(int i = 0; i < n; i++) {
		if(a[i] & p) ones.emplace_back(a[i] % p);
		else zeros.emplace_back(a[i] % p);
	}
	sort(ones.begin(), ones.end());
	sort(zeros.begin(), zeros.end());
	vector<pair<int, int>> p_ones = parse(ones), p_zeros = parse(zeros);
	return get_crossed(p_ones, p_zeros, p) + get_pairs(p_ones, p) + get_pairs(p_zeros, p);
}

int main(){
	scanf("%d", &n);
	int X = 0, A = INT_MAX, O = 0;
	for(int i = 0; i < n; i++) {
		scanf("%d", a + i);
		X ^= a[i] << 1;
		A &= a[i] << 1;
		O |= a[i] << 1;
	}
	for(int b = 0, p = 1; b < 31; b++, p <<= 1) {
		long long cnt = get_bits(b, p);
	/*	long long cnt2 = 0;
		for(int i = 0; i < n; i++) {
			for(int j = i + 1; j < n; j++) {
				if((a[i] + a[j]) & p) cnt2 += 1;
			}
		}
		cerr << p << " -> " << cnt << " vs " << cnt2 << endl;*/
		if(cnt & 1) X ^= p;
		if(cnt != 1ll * n * (n - 1) / 2) A &= ~p;
		if(cnt) O |= p;
	}
	printf("%d\n", X);
	return 0;
}

Compilation message (stderr)

xorsum.cpp: In function 'std::vector<std::pair<int, int> > parse(std::vector<int>&)':
xorsum.cpp:12:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |  while(l < v.size()) {
      |        ~~^~~~~~~~~~
xorsum.cpp:14:11: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |   while(r < v.size() and v[l] == v[r]) r += 1;
      |         ~~^~~~~~~~~~
xorsum.cpp: In function 'long long int get_pairs(std::vector<std::pair<int, int> >, int)':
xorsum.cpp:44:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |  for(int i = 0; i < v.size(); i++) {
      |                 ~~^~~~~~~~~~
xorsum.cpp: In function 'int main()':
xorsum.cpp:75:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   75 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
xorsum.cpp:78:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   78 |   scanf("%d", a + i);
      |   ~~~~~^~~~~~~~~~~~~

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