Submission #630009

#	Time	Username	Problem	Language	Result	Execution time	Memory
630009		czhang2718	Election (BOI18_election)	C++17	0 / 100	2 ms	588 KiB

election

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

const int K=19;
int n, q;

// get INDEX of min in [l,r]
struct st{
  vector<int> a;
  vector<vector<int>> mn;

  st(vector<int> a){
    this->a=a;
    mn.resize(K, vector<int>(n+1));
    for(int i=1; i<=n; i++){
      mn[0][i]=a[i];
    }
    for(int j=1; j<K; j++){
      for(int i=0; i+(1<<j)<=n+1; i++){
        mn[j][i]=min(mn[j-1][i], mn[j-1][i+(1<<(j-1))]);
      }
    }
  }

  int qry(int l, int r){
    int v=1e9;
    int i=l;
    for(int k=0; k<K; k++){
      if((r-l+1)&(1<<k)){
        v=min(v, mn[k][i]);
        i+=(1<<k);
      }
    }
    // cout << "mn " << l << " " << r << " " << v << "\n";
    i=l;
    for(int k=K-1; k>=0; k--){
      if(i+(1<<k)>r+1) continue;
      if(mn[k][i]>v) i+=(1<<k);
    }
    return i;
  }
};

int main(){
  cin.tie(0)->sync_with_stdio(0);

  cin >> n;
  vector<int> a(n+1), b(n+1);
  for(int i=1; i<=n; i++){
    char c; cin >> c;
    a[i]=(c=='C'?1:-1);
  }
  for(int i=n; i>=1; i--){
    b[i]=a[n+1-i];
  }
  for(int i=1; i<=n; i++){
    a[i]+=a[i-1];
    b[i]+=b[i-1];
  }

  st st1(a), st2(b);

  cin >> q;
  while(q--){
    int l,r;
    cin >> l >> r;
    int i=st1.qry(l-1,r);
    int j=n-st2.qry(n-r, n+1-l);
    // cout << "ij " << i << " " << j << "\n";
    if(i<j) cout << a[l-1]-a[i]+a[j]-a[r] << "\n";
    else{
      // cout << a[n-st2.qry(n-r, n-i)] << "\n";
      cout << a[l-1]-a[i]+max(a[j]-a[l-1]-(a[r]-a[i]), a[n-st2.qry(n-r, n-i)]-a[r]) << '\n';
    }
  }
}
// we're just a room full of strangers

• Subtask 1: 0 / 28
• Subtask 2: 0 / 54
• Subtask 3: 0 / 18