Submission #1252656

#	Time	Username	Problem	Language	Result	Execution time	Memory
1252656		fahmid_rng	Finding Routers (IOI20_routers)	C++20	100 / 100	1 ms	328 KiB

routers

#include<bits/stdc++.h>
#include "routers.h"
using namespace std;
std::vector<int> find_routers(int l, int n, int q) {
    vector<int> p(n),left(n),right(n,l);
    //we want to modify left and right in such a way that left[i] denotes the last index, k for which use_detector(k)=i-1 & right[i] denotes the first index for which use_detector(k)=i
    p[0]=0;
    for(int i=1;i<n;++i){
      left[i]=i-1;
    }
    for(int i=1;i<n;++i){
      left[i]=max(p[i-1]+1,left[i]);
      while(right[i]-left[i]>1){
        int mid=(left[i]+right[i])/2;
        int q=use_detector(mid);
        left[q+1]=mid;
        for(int j=i;j<=q;++j){
          right[j]=mid;
        }
      }
      p[i]=2*left[i]-p[i-1];
      //this is true because left[i]=(p[i]+p[i-1])/2 by definition i.e left[i] is exactly in the middle of p[i-1] & p[i]
    }
    return p;
  }

• Subtask 1: 16 / 16
• Subtask 2: 21 / 21
• Subtask 3: 23 / 23
• Subtask 4: 40 / 40