LIS

Posted 2020-09-18 wqkant

public class LISEfficient {
  public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();    //number of elements
      int[] ar = new int[n];     //input elements
      for (int i=0; i<n; i++) {
          ar[i] = sc.nextInt();
      }

      System.out.println(lis2(ar));       //returns the size of LIS
  }

  static int lis2(int[] ar){
      TreeSet<Integer> set = new TreeSet<Integer>();
      for (int i=0; i<ar.length; i++) {
          Integer ceil = set.ceiling(ar[i]);
          if(ceil == null)     //if ceil not present this simply extends the current sequence
              set.add(ar[i]);
          else{                   //replace ceil with this value
              set.remove(ceil);
              set.add(ar[i]);
          }
      }
      return set.size();
  }
}