Submission #778965

#	Time	Username	Problem	Language	Result	Execution time	Memory
778965		magician	Longest beautiful sequence (IZhO17_subsequence)	C++14	0 / 100	2 ms	472 KiB

subsequence

#include<iostream>
#include<vector>
#include<algorithm>
#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
using namespace std;

const int N = (int)1e5 + 1;

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

bool maximize(int& a, const int& b) {
  if(a < b) {
    a = b;
    return true;
  }
  return false;
}

void print_ans(vector<int>& ans) {
  cout << ans.size() << '\n';
  for(int i = 0; i < (int)ans.size(); i++) cout << ans[i] << ' ';
  cout << '\n';
}

int brute_force(void) {
  vector<int> f(n + 1, 0), trace(n + 1, -1);
  int p = 1;
  for(int i = 1; i <= n; i++) {
    f[i] = 1;
    trace[i] = -1;
    for(int j = 1; j < i; j++) {
      if(__builtin_popcount(a[i] & a[j]) == k[i]) {
        if(maximize(f[i], f[j] + 1)) {
          trace[i] = j;
        }
      }
    }
    if(f[i] > f[p]) p = i;
  }
  vector<int> ans;
  for(int i = p; i != -1; i = trace[i]) {
    ans.push_back(i);
  }
  reverse(ans.begin(), ans.end());
  print_ans(ans);
}

void slow_bitmask_dp(void) {
  vector<pair<int, int> > f(MASK(20), make_pair(0, -1));
  vector<int> trace(n + 1, -1);
  int p = 0;
  for(int i = 1; i <= n; i++) {
    if(maximize(f[a[i]].first, 1)) {
      f[a[i]].second = i;
    }
    for(int mask = 0; mask < MASK(20); mask++) {
      if(__builtin_popcount(mask & a[i]) == k[i]) {
        if(maximize(f[a[i]].first, f[mask].first + 1)) {
          f[a[i]].second = i;
          trace[i] = f[mask].second;
        }
      }
    }
    if(f[a[i]] > f[p]) p = a[i];
  }
  vector<int> ans;
  for(int i = p; i != -1; i = trace[i]) {
    ans.push_back(i);
  }
  reverse(ans.begin(), ans.end());
  print_ans(ans);
}

int main(void) {
  ios_base::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);

  // freopen("a.in", "r", stdin); freopen("a.out", "w", stdout);

  cin >> n;
  for(int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for(int i = 1; i <= n; i++) {
    cin >> k[i];
  }

  if(n <= 5000) {
    brute_force();
  }
  else if(*max_element(a + 1, a + n + 1) < MASK(8)) {
    slow_bitmask_dp();
  }
  else {
    return 1;
  }
}

Compilation message (stderr)

subsequence.cpp: In function 'int brute_force()':
subsequence.cpp:48:1: warning: no return statement in function returning non-void [-Wreturn-type]
   48 | }
      | ^

• Subtask 1: 0 / 7
• Subtask 2: 0 / 16
• Subtask 3: 0 / 17
• Subtask 4: 0 / 60