Error Unhandled Exception: System.IndexOutOfRangeException?

Question

Error Index was outside the bounds of the array. Program is to remove duplicates from an array I understand the error which is that line 32 where an extra element is created at the end of the for loop but i am unable to figure out a way to display the whole array without the duplicates. What the prog is suppose to do is inputs a 5 number into an array and then sorts them and if their are duplicates it removes it. I hope i made it clear!

     using System;

     class duplicate 
     {
        static void Main() 
        {
            const int Array_Size = 5;
            int [] number = new int [Array_Size];
            int i;

    for ( i = 0; i < Array_Size; i++) 
    {
        number[i] = Int32.Parse(Console.ReadLine());
        if (number[i] < 9 || number[i] > 101)
        {
            Console.WriteLine("Enter Number between 10 - 100");
            number[i] = Int32.Parse(Console.ReadLine());
        }
    }

    Array.Sort(number);

    Console.WriteLine("Sorted Array : ");

    for (i = 0; i < Array_Size; i++)
    {
        Console.WriteLine("Element is " + number[i]);
    }

    Console.WriteLine("Duplicate Removed : ");

    for (i = 0; i < Array_Size; i++)
    { 
        if (number[i] != number[i+1])
            Console.WriteLine("Element is " + number[i]);
    }

    Console.ReadLine();
}

}

goric · Accepted Answer · 2013-03-16 16:25:40Z

2

The exception is happening at this line:

if (number[i] != number[i+1])

On the final iteration of your loop, that line will resolve to:

if(number[4] != number[5])

Since your array only has 5 items in it and is 0-based, number[5] results in your IndexOutOfRange exception.

If you're trying to compare every item to the one after it, simply don't check on the final iteration:

if(i != Array_Size && number[i] != number[i+1])

Or only loop up to Array_Size - 1:

for (i = 0; i < Array_Size - 1; i++)

edited Mar 16, 2013 at 16:25

answered Mar 16, 2013 at 16:19

goric

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Comments

MarcinJuraszek · Accepted Answer · 2013-03-16 16:18:11Z

1

You can use LINQ to get distinct values from an Array:

var distinct = number.Distinct().ToArray();

You need using System.Linq; on top of your file to make it work.

And to make it clear: your Exception comes from here:

for (i = 0; i < Array_Size; i++)
{ 
    if (number[i] != number[i+1])
        Console.WriteLine("Element is " + number[i]);
}

When i == Array_Size -1 (which is the last pass) number[i+1] does not exist.

answered Mar 16, 2013 at 16:18

MarcinJuraszek

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Steve · Accepted Answer · 2013-03-16 16:24:41Z

0

Of course Linq is the way to go today, but you could still use the old fashioned loop

int prev = number[0];
Console.WriteLine("Element is " + prev);
for (int i = 1; i < Array_Size; i++)
{ 
    int cur = number[i];
    if (cur != prev)
    {
        Console.WriteLine("Element is " + cur);
        prev = cur;
    }
}

answered Mar 16, 2013 at 16:24

Steve

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Comments

JaredPar · Accepted Answer · 2013-03-16 16:19:50Z

0

This if statement is simply unsafe

for (i = 0; i < Array_Size; i++) {
   if (number[i] != number[i+1])
     ...

The final value of i in the loop will be Array_Size - 1 hence i + 1 isn't a legal index into the array. To fix this just change the constraint on the for loop such that i + 1 is always a legal index

for (i = 0; i < Array_Size - 1; i++)

answered Mar 16, 2013 at 16:19

JaredPar

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1 Comment

user1905501 Over a year ago

If i use for (i = 0; i < Array_Size - 1; i++) It doesn't display the last element

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