Dynamic programming

#include <iostream>
#include <string.h>
using namespace std;


        int ceilIdx(int tail[], int l, int r, int key) 
        { 
            while (r > l) {         
                int m = l + (r - l) / 2; 
                if (tail[m] >= key) 
                    r = m; 
                else
                    l = m+1; 
            } 
      
            return r; 
        } 
  
    int LIS(int arr[], int n) 
    { 
     
  
        int tail[n]; 
        int len =1; 
  
        tail[0] = arr[0]; 
        
        for (int i = 1; i < n; i++) {
            
            if(arr[i] > tail[len - 1])
            {
                tail[len] = arr[i];
                len++;
            }
            else{
                int c = ceilIdx(tail, 0, len - 1, arr[i]);
                
                tail[c] = arr[i];
            }
        } 
  
        return len; 
    } 


int main() {
	
	
 int arr[] ={3, 10, 20, 4, 6, 7};
  int n = 6;

cout<<LIS(arr, n);
	

}