Submission #538503

#	Time	Username	Problem	Language	Result	Execution time	Memory
538503		cig32	Building 4 (JOI20_building4)	C++17	100 / 100	518 ms	70284 KiB

building4

#include "bits/stdc++.h"
using namespace std;
const int MAXN = 2e5 + 10;
const int MOD = 1e9 + 7;
#define int long long
#define ll __int128
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
  int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
ll read() { // read int128
  int x; cin >> x; return (ll)x;
}
long long bm(long long b, long long p) {
  if(p==0) return 1 % MOD;
  long long r = bm(b, p >> 1);
  if(p&1) return (((r*r) % MOD) * b) % MOD;
  return (r*r) % MOD;
}
long long inv(long long b) { 
  return bm(b, MOD-2);
}
long long f[MAXN];
long long nCr(int n, int r) { 
  long long ans = f[n]; ans *= inv(f[r]); ans %= MOD;
  ans *= inv(f[n-r]); ans %= MOD; return ans;
}
void precomp() { 
  for(int i=0; i<MAXN; i++) f[i] = (i == 0 ? 1 % MOD : (f[i-1] * i) % MOD);
}
pair<int, int> seg_union(vector<pair<int,int> > v) {
  int mi = 1e9, ma = -1e9;
  for(auto x: v) mi = min(mi, x.first), ma = max(ma, x.second);
  if(ma == -1e9) return {-1, -1};
  return {mi, ma};
}
void solve(int tc) {
  int n;
  cin >> n;
  int a[2*n + 1], b[2*n + 1];
  for(int i=1; i<=2*n; i++) cin >> a[i];
  for(int i=1; i<=2*n; i++) cin >> b[i];
  int la[2*n + 1], ra[2*n + 1], lb[2*n + 1], rb[2*n + 1];
  for(int i=1; i<=2*n; i++) la[i] = ra[i] = lb[i] = rb[i] = -1;
  la[1] = ra[1] = 1;
  lb[1] = rb[1] = 0;
  for(int i=2; i<=2*n; i++) {
    vector<pair<int, int> > A, B;
    if(a[i-1] <= a[i] && la[i-1] != -1) {
      A.push_back({la[i-1] + 1, ra[i-1] + 1});
    }
    if(b[i-1] <= a[i] && lb[i-1] != -1) {
      A.push_back({lb[i-1] + 1, rb[i-1] + 1});
    }
    if(a[i-1] <= b[i] && la[i-1] != -1) {
      B.push_back({la[i-1], ra[i-1]});
    }
    if(b[i-1] <= b[i] && lb[i-1] != -1) {
      B.push_back({lb[i-1], rb[i-1]});
    }
    pair<int, int> resa = seg_union(A);
    pair<int, int> resb = seg_union(B);
    la[i] = resa.first, ra[i] = resa.second;
    lb[i] = resb.first, rb[i] = resb.second;
  }
  if(la[2*n] <= n && n <= ra[2*n]) {
    stack<char> st;
    char cur = 'A';
    int tar = n;
    for(int i=2*n; i>=1; i--) { 
      st.push(cur);
      // find tar!!
      if(cur == 'A') tar--;
      if(la[i-1] <= tar && tar <= ra[i-1] && a[i-1] <= (cur == 'A' ? a[i] : b[i])) cur = 'A';
      else cur = 'B';
    }
    while(st.size()) {
      cout << st.top();
      st.pop();
    }
    cout << '\n';
  }
  else if(lb[2*n] <= n && n <= rb[2*n]) {
    stack<char> st;
    char cur = 'B';
    int tar = n;
    for(int i=2*n; i>=1; i--) { 
      st.push(cur);
      // find tar!!
      if(cur == 'A') tar--;
      if(la[i-1] <= tar && tar <= ra[i-1] && a[i-1] <= (cur == 'A' ? a[i] : b[i])) cur = 'A';
      else cur = 'B';
    }
    while(st.size()) {
      cout << st.top();
      st.pop();
    }
    cout << '\n';
  }
  else {
    cout << "-1\n";
  }
}
int32_t main(){
  precomp();
  ios::sync_with_stdio(0); cin.tie(0);
  int t = 1; //cin >> t;
  for(int i=1; i<=t; i++) solve(i);
} 

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89