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C#

Marko Rapaic
Marko Rapaic
13,871 Points
Posted by Marko Rapaic
Marko Rapaic
13,871 Points

Intermediate C# Challenge Task 3 of 3

So i've attempted this challenge with my code below. This successfully detects if an index item is preceded by a duplicate item, and then returns an appropriate bool value. You can see this in the stack trace output below.

When I initially got the System.IndexOutOfRangeException I added the check in the if statement i != 0 so that if the index was 0, it wouldn't try looking outside of the array.

I've added some Console.WriteLine() statements to show what's happening - you can see that it tries to go through the array twice for some reason, but crashes on the second attempt. I also tried discovering the length of sequence and it came back with two seperate values....

Either way, not sure what the issue is, and would appreciate some fresh eyes :)

My code attempt:

namespace Treehouse.CodeChallenges
{
    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {
            bool isDuplicateFound = false;

            foreach (int i in sequence)
            {
                    System.Console.WriteLine(i);

                    if ((sequence[i] == sequence[i-1]) && (i != 0)) 
                    {
                        System.Console.WriteLine(i + " is a repeated value!");
                        isDuplicateFound = true;
                    }
            }

            System.Console.WriteLine("Duplicates found? " + isDuplicateFound + ".");
            return isDuplicateFound; 
        }
    }
}

Stack trace output:

1
2
3
3 is a repeated value!
3
3 is a repeated value!
4
Duplicates found? True.
1
2
3
4
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.IndexOutOfRangeException: Index was outside the bounds of the array.
  at Treehouse.CodeChallenges.RepeatDetector.Scan (System.Int32[] sequence) <0x41bb71c0 + 0x0005d> in :0 
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00038] in /builddir/build/BUILD/mono-4.4.1/mcs/class/corlib/System.Reflection/MonoMethod.cs:295 
  --- End of inner exception stack trace ---
  at Treehouse.CodeChallenges.Helpers.ReflectionHelpers.Call[T] (System.Reflection.MethodInfo method, System.Object instance, System.Object[] args) <0x41bb69d0 + 0x00027> in :0 
  at MonoTester.Run () [0x00130] in MonoTester.cs:104 
  at MonoTester.Main (System.String[] args) [0x00013] in MonoTester.cs:29

3 Answers

Marko Rapaic
Marko Rapaic
13,871 Points
Marko Rapaic
Marko Rapaic
13,871 Points

Nevermind, got it working with the following:

namespace Treehouse.CodeChallenges
{
    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {  
            // Begin initial for loop, assigning each index value to i as it loops.
            for (int i = 0; i < sequence.Length; i++)
            {
                // Secondary for loop is used to add 1 to the previous for loop.
                for (int j = i + 1; j < sequence.Length; j++)
                {
                    // If the items at the same index in each array are the same, then a duplicate has been found.
                    if (sequence[i] == sequence[j]) return true;
                }
            }
            return false;
        }
    }
}
Michele Morison
Michele Morison
13,407 Points
Michele Morison
Michele Morison
13,407 Points

This worked for me in VS

namespace ConsoleApplication4 { class RepeatDetector : SequenceDetector { public override bool Scan(int[] sequence) { for (int i = 1; i == sequence.Length; i++) { if (sequence[i] == sequence[(i-1)]) { return true; } } return false; } } }

Chris Burbage
PLUS
Chris Burbage
Courses Plus Student 4,693 Points
Chris Burbage
Chris Burbage
Courses Plus Student 4,693 Points

namespace Treehouse.CodeChallenges { class RepeatDetector : SequenceDetector { public override bool Scan(int[] sequence) { bool duplicateFound = false; for (int i=1; i< sequence.Length; i++) { if (sequence[i]==sequence[i-1]) duplicateFound = true; } return duplicateFound; } } }