Submission #699809

#	Time	Username	Problem	Language	Result	Execution time	Memory
699809		Abrar_Al_Samit	Boat (APIO16_boat)	C++17	100 / 100	1798 ms	65668 KiB

boat

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

#define ub upper_bound
const int nax = 503;
const int mod = 1e9 + 7;
const int cax = 1e6 + 3;
const long long sux = 103217;

vector<int>ind[nax*2];
int a[nax], b[nax];
int n, m;
int dp[nax*2][nax];
int inv[nax];
int fac[nax], iv[nax];
vector<int>imp;

int add(int a, int b) {
  a += b;
  if(a>=mod) a -= mod;
  return a;
}
int mul(int a, int b) {
  return (a * 1LL * b) % mod;
}
int quickpow(int a, int b) {
  int ret = 1;
  while(b) {
    if(b&1) ret = mul(ret, a);
    a = mul(a, a);
    b >>= 1;
  }
  return ret;
}
vector<pair<long long,int>>table[cax];
int C(int n, int r) {
  if(n<nax) {
    return mul(fac[n], mul(iv[r], iv[n-r]));
  }

  long long H = n * sux + r;
  int H2 = H % cax;
  for(auto x : table[H2]) {
    if(x.first==H) return x.second;
  }


  int ret = 1;
  for(int i=n-r+1; i<=n; ++i) {
    ret = mul(ret, i);
  }
  for(int i=1; i<=r; ++i) {
    ret = mul(ret, inv[i]);
  }
  table[H2].emplace_back(H, ret);
  return ret;
}

vector<pair<long long,int>>andp[cax];
int get(int len, int op) {
  long long H = len * sux + op;
  int H2 = H % cax;
  for(auto x : andp[H2]) {
    if(x.first==H) return x.second;
  }

  int ret = 0;
  for(int take=0, to=min(op, len-1); take<=to; ++take) {
    ret = add(ret, mul(C(op, take), C(len, take+1)));
  }

  andp[H2].emplace_back(H, ret);
  return ret;
}
int solve(int i, int prv) {
  if(i==m-1) return prv>0;
  int &ret = dp[i][prv];
  if(ret!=-1) return ret;
  ret = 0;

  ret = solve(i+1, prv);
  int len = imp[i+1]-imp[i];

  for(int mx=ub(ind[i].begin(), ind[i].end(), prv)-ind[i].begin(), 
    cur_op=0, sz=ind[i].size(); mx<sz; ++mx, ++cur_op) {

    if(ind[i][mx]<=prv) continue;

    int cur = mul(solve(i+1, ind[i][mx]), get(len, cur_op));
    ret = add(ret, cur);
  }
  return ret;
}
void PlayGround() {
  cin>>n;
  set<int>pts;
  for(int i=1; i<=n; ++i) {
    cin>>a[i]>>b[i];
    pts.insert(a[i]);
    pts.insert(b[i]+1);
  }

  for(int x : pts) {
    imp.push_back(x);
  } 
  m = imp.size();
  for(int i=0; i<m; ++i) {
    for(int j=1; j<=n; ++j) {
      if(imp[i]>=a[j] && imp[i]<=b[j]) {
        ind[i].push_back(j);
      }
    }
  }
  for(int i=1; i<nax; ++i) {
    inv[i] = quickpow(i, mod-2);
  }
  fac[0] = iv[0] = 1;
  for(int i=1; i<nax; ++i) {
    fac[i] = mul(i, fac[i-1]);
    iv[i] = mul(iv[i-1], inv[i]);
  }
  memset(dp, -1, sizeof dp);
  cout<<solve(0, 0)<<'\n';


  // cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  PlayGround();
  return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42