Index out of range exception on array

Question

I'm trying to reverse an array. This is my code:

using System;

class Hello
{
    static void Main()
    {
        int[] num  = new int[] { 1, 2, 3, 4, 5 };
        int index = num.Length - 1;
        int[] newNum = new int[index];

        for (int i = 0; i < num.Length; i++)
        {
            newNum[i] = num[index];  // error     
            index--;        
            Console.WriteLine(newNum[i]);
        }
        Console.ReadLine();
    }
}

When I run the code, the console prints

and then returns an error:

IndexOutOfRangeException was unhandled

on the line:

newNum[i] = num[index];

What's wrong with that line of code? When I print num[0] before that for loop it works fine.

Well yes, your `newNum` array is one element smaller than your `num` array, but your loop is written as if it's the same length as `num`. Why are you doing that? — Jon Skeet, Dec 03 '15 at 12:20
Why not use Enumerable.Reverse? [link](https://msdn.microsoft.com/library/bb358497(v=vs.100).aspx) — Chris Davis, Dec 03 '15 at 12:20
@croxy: Please don't remove relevant code. The `using` directive for the `System` namespace is necessary to make this code compile. — Jon Skeet, Dec 03 '15 at 12:21
@JonSkeet Oops, I'm sorry my mistake. Will not happen again. — croxy, Dec 03 '15 at 12:23

score 0 · Accepted Answer · answered Dec 03 '15 at 12:23

0

length of your new array is 4. that's mean I'll cover from 0 to 3

int[] newNum = new int[index];

and your loop will go i=4

when i will 4 your code will collapse. as newNum support only to 3rd index.

this should be

int[] newNum = new int[index+1];

answered Dec 03 '15 at 12:23

Anik Islam Abhi

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Index out of range exception on array

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