Submission #748120

#	Time	Username	Problem	Language	Result	Execution time	Memory
748120		Sam_a17	Group Photo (JOI21_ho_t3)	C++17	100 / 100	1137 ms	393116 KiB

Main

#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
//#include "temp.cpp"
#include <cstdio>
using namespace std;
 
#ifndef ONLINE_JUDGE
#define dbg(x) cerr << #x <<" "; print(x); cerr << endl;
#else
#define dbg(x)
#endif
 
#define sz(x) (int((x).size()))
#define len(x) (int)x.length()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define clr(x) (x).clear()
#define uniq(x) x.resize(unique(all(x)) - x.begin());
 
#define pb push_back
#define popf pop_front
#define popb pop_back
 
void print(long long t) {cerr << t;}
void print(int t) {cerr << t;}
void print(string t) {cerr << t;}
void print(char t) {cerr << t;}
void print(double t) {cerr << t;}
void print(long double t) {cerr << t;}
void print(unsigned long long t) {cerr << t;}
 
template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T> void print(T v[],T n) {cerr << "["; for(int i = 0; i < n; i++) {cerr << v[i] << " ";} cerr << "]";}
template <class T, class V> void print(pair <T, V> p) {cerr << "{"; print(p.first); cerr << ","; print(p.second); cerr << "}";}
template <class T> void print(vector <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(deque <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(set <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(multiset <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T, class V> void print(map <T, V> v) {cerr << "[ "; for (auto i : v) {print(i); cerr << " ";} cerr << "]";}
 
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define nl '\n'
 
// for random generations
mt19937 myrand(chrono::steady_clock::now().time_since_epoch().count());
// mt19937 myrand(131);

// for grid problems
int dx[8] = {-1,0,1,0,1,-1,1,-1};
int dy[8] = {0,1,0,-1,1,1,-1,-1};
 
// lowest / (1 << 17) >= 1e5 / (1 << 18) >= 2e5 / (1 << 21) >= 1e6
void fastIO() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr); cout.tie(nullptr);
}
// file in/out
void setIO(string str = "") {
  fastIO();
 
  if (str != "") {
    freopen((str + ".in").c_str(), "r", stdin);
    freopen((str + ".out").c_str(), "w", stdout);
  }
}
// Indexed Set
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int N = 5005;

// bit
struct fenwick {
  int size;
  vector<long long> tree; 

  void init(int size_) {
    tree.assign(size_ + 2, 0);
    size = size_;
  }

  void upd(int u, long long v) {
    while(u <= size) {
      tree[u] += v;
      u += u & (-u);
    }
  }

  long long qry(int u) {
    long long sum = 0;
    while(u > 0) {
      sum += tree[u];
      u -= u & (-u); // lsb
    }
    return sum;
  }

  long long sum(int l, int r) {
    return qry(r) - qry(l - 1);
  }

};

int n, pos[N];

int get(vector<int>& a, vector<int>& b) {
  fenwick ft;
  ft.init(n + 1);

  int ans = 0;
  for(int i = 0; i < n; i++) {
    int wh = pos[b[i]];
    ans += wh - 1 - ft.qry(wh);
    ft.upd(wh, 1);
  }

  return ans;
}

int dp[N];

int rec(int to) {
  if(to == 0) {
    return 0;
  }

  if(dp[to] != -1) {
    return dp[to];
  }

  int maxi = n - (n - to);

  fenwick ft, nft;
  ft.init(n + 1);
  nft.init(n + 1);
  for(int i = maxi + 1; i <= n; i++) {
    ft.upd(pos[i], 1);
  }

  int put = n * n;
  int sm = 0;
  for(int i = to; i >= 1; i--) {
    // fenwick nft = ft;

    int nd = to - i;
    int cur = maxi - nd;
    // dbg(cur)

    sm += n - pos[cur];
    sm -= ft.sum(pos[cur], n);
    sm += nft.sum(pos[cur], n);
    ft.upd(pos[cur], 1);

    sm -= nft.qry(pos[cur]);
    nft.upd(pos[cur], 1);
    
    // for(int j = to; j >= i; j--, cur++) {
    //   int suf = n - pos[cur];
    //   suf -= nft.sum(pos[cur], n);
    //   nft.upd(pos[cur], 1);
    //   sm += suf;
    // }

    // dbg(sm)
    put = min(put, sm + rec(i - 1));
  }

  dp[to] = put;
  return dp[to];
}

void solve_() {
  cin >> n;
  vector<int> a(n);

  for(int i = 0; i < n; i++) {
    cin >> a[i];
    pos[a[i]] = i + 1;
  }

  for(int i = 0; i <= n; i++) {
    dp[i] = -1;
  }

  // dbg(rec(3))
  cout << rec(n) << '\n';
}

int main() {
  setIO();
  
  auto solve = [&](int test_case)-> void {
    while(test_case--) {
      solve_();
    }

  };
 
  int test_cases = 1; 
  // cin >> test_cases;
  solve(test_cases);
 
  return 0;
}

Compilation message (stderr)

Main.cpp: In function 'void setIO(std::string)':
Main.cpp:67:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |     freopen((str + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:68:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |     freopen((str + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36