Recursive via Binary Search Help(Java)

Question

We was told to make a binary search with the class Recursion. However I'm stuck as the recursion isn't working properly according to my professor(Didn't elaborate when I asked for help) and been working with a fellow student. We come to the conclusion of needing int count but I'm not sure where or how to implement it. Java isn't my strongest language so a guide or hint would be very helpful.

            public class Recursive {
            public int BinarySearch(int x[], int target, int low, int high)
            {
               if (low >= high) return -1; 
               int mid = (low + high)/2;
               if (x[mid] > target)
                  return BinarySearch(x, target, low, mid-1); 
               else if (x[mid] < target)
                  return BinarySearch(x, target, mid+1, high); ;
               return mid;
            }
            public int firstNnumber(int n)
            {
               if (n < 1) return 0;
               return firstNnumber(n-1) + n;
            }
            public int firstNnumber2(int n)
            {
               if (n==1) return 1;
               if (n==2) return 3;
               boolean even = (n%2 == 0);
               n /= 2;
               if (even)
               {
                   return 2*firstNnumber2(n) + n*n;
               }
               else
                   return 2*firstNnumber2(n) + (n + 1)*(1+n);
            }
            public int gaussian(int n)
            {
               return  n*(n+1)/2;
            }

            static public void main(String [] args)
            {
               Recursive r = new Recursive();
               System.out.println("By Gussain, Sum of first 100000 integers=" + r.gaussian(10000));
               System.out.println("By recurssion 2,    Sum of first 100000 integers=" + r.firstNnumber2(6)); 
            }


            }

This is what is printed, I don't understand what's the problem with my code.

By Gussain, Sum of first 100000 integers=50005000 By recurssion 2, Sum of first 100000 integers=21

mehdi maick · Accepted Answer · 2019-02-01 18:57:50Z

1

your are calling with the wrong params, try calling with

static public void main(String [] args){
  Recursive r = new Recursive();
  System.out.println("By Gussain, Sum of first 100000 integers=" + r.gaussian(10000));
  System.out.println("By recurssion 2,    Sum of first 100000 integers=" + r.firstNnumber2(10000)); 
}

answered Feb 1, 2019 at 18:57

mehdi maick

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1 Comment

hanoldaa Over a year ago

This will fix the output. repl.it/repls/PureFlakyTransversals tested and both outputs are the same

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