Submission #390036

#	Time	Username	Problem	Language	Result	Execution time	Memory
390036		acm	XOR Sum (info1cup17_xorsum)	C++14	100 / 100	1473 ms	73836 KiB

xorsum

#include <bits/stdc++.h>
#define speed                   \
  ios_base::sync_with_stdio(0); \
  cin.tie(0);                   \
  cout.tie(0);
#define precision     \
  cout.precision(30); \
  cerr.precision(10);
#define ll long long
#define ld long double
#define pll pair<ll, ll>
#define pii pair<int, int>
#define forn(n) for (int i = 1; i <= n; i++)
#define forlr(l, r) for (int i = l; i != r; (l > r ? i-- : i++))
#define pb(x) push_back(x)
#define sz(x) (int)x.size()
#define mp(x, y) make_pair(x, y)
#define all(x) x.begin(), x.end()
#define pc(x) __builtin_popcount(x)
#define pcll(x) __builtin_popcountll(x)
#define F first
#define S second
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
void ioi(string name) {
  freopen((name + ".in").c_str(), "r", stdin);
  freopen((name + ".out").c_str(), "w", stdout);
}
int n, d, a[1000005], b[1000005], c[32000005];
int get(int x) {
  int e = 0, f = n;
  for (int i = 1; i <= n; i++) {
    while (f && b[i] + b[f] > x) f--;
    if (i < f) e ^= (f - i) & 1;
  }
  return e;
}
int f(int x) {
  for (int i = 1; i <= n; i++) b[i] = (a[i] & ((1 << (x + 1)) - 1));
  if ((1 << (x + 1)) > 2 * n * __lg(n) || (1 << (x + 1)) > 32000000) {
    sort(b + 1, b + n + 1);
  } else {
    int e = 0;
    for (int i = 1; i <= n; i++) c[b[i]]++;
    for (int i = 0; i < (1 << (x + 1)); i++)
      while (c[i]) b[++e] = i, c[i]--;
  }
  return (get((1 << x) - 1) ^ get((1 << (x + 1)) - 1) ^
          get((1 << x) + (1 << (x + 1)) - 1) ^ get((1 << (x + 2)) - 1));
}
int main() {
  speed;
  precision;
  // code
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i], d ^= (a[i] + a[i]);
  for (int i = 0; i <= 29; i++) d ^= f(i) * (1 << i);
  cout << d;
  // endl
#ifndef ONLINE_JUDGE
  cerr << "\nTime elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
  return 0;
}

Compilation message (stderr)

xorsum.cpp: In function 'void ioi(std::string)':
xorsum.cpp:26:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   26 |   freopen((name + ".in").c_str(), "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
xorsum.cpp:27:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   27 |   freopen((name + ".out").c_str(), "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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