Question

I was following a tutorial showing how to create a Binary search algorithm from scratch. However I recieve the error “Use of unassigned local variable ‘Pivot'”. I’m new to the language and have only tried much simpler languages previously.

I apologise for the lack of internal documentation and appauling use of white space.

The error is near the bottom of the code labled using “//”

Here is the program:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Binary_Search_2
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] arr = new int[10];

            Random rnd = new Random();

            for (int i = 0; i < arr.Length; i++)
            {
                arr[i] = rnd.Next(1, 10);
            }

            Array.Sort(arr);
            for (int i = 0; i < arr.Length; i++)
            {
                Console.Write("{0},", arr[i]);
            }
            int Start = 0;
            int End = arr.Length;
            int Center = Start + End / 2;

            int Pivot;

            while (arr[6] > 0)
            {
                while (arr[6] < arr[Center])
                {
                    End = Center;
                    Center = (End + Start) / 2;
                    if (Pivot == arr[Center])
                    {
                        Console.WriteLine("The Index is {0}", arr[Center]);
                    }
                    break; 
                }

                while (arr[6] > arr[Center])
                {
                    Start = Center;
                    Center = (End + Start) / 2;
                    if (Pivot == arr[Center])  //**This is where the error occurs.** 
                    {
                        Console.WriteLine("The index is {0}", arr[Center]);
                    }
                }
            }
        }
    }
}

I’m sorry if this is actually something really simple but I don’t have anyone to teach me directly and I’m out of ideas.

Answer 1

The error is caused by this line:

int Pivot;

The value of Pivot needs to be set before using it in an if statement.

This indicates an error in your code: you check Pivot''s value in anif` statement, but you never assign to it. Look through the tutorial to find a line that looks like this:

Pivot = ... // <<=== some expression here

Most likely, you did not enter this line into your program when you followed the tutorial.