Am I acessing the values in the array correctly?

Question

Hi,

I tried to solve this problem in two ways, using a for() loop and another way using a foreach() loop (commented bellow)

It seems to me that it should work, can you help me?

Thanks :)

SequenceDetector.cs

namespace Treehouse.CodeChallenges
{
    class SequenceDetector
    {
        public virtual bool Scan(int[] sequence)
        {
            return true;
        }
    }
}

RepeatDetector.cs

namespace Treehouse.CodeChallenges
{
    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {
            int i = 1;

            //use a for loop
            for(i=0; i < sequence.Length; i++)
            {
                    // comparing the actual value in the array with the previous one
                    if(i > 0 && sequence[i] == sequence[i-1])
                    {
                        return true;
                    }
                    else
                    {
                        return false;
                    }
            }

            /*
            // use a foreach loop 
            foreach(int val in sequence)
            {
                // comparing the actual value in the array with the previous one
                if( sequence[i] == sequence[i-1] )
                {
                    // return true if it is the same
                    return true;
                }
                else
                {
                    return false;
                }

                i++;
            }
            */
        }
    }
}

Answer 1 · 2018-05-09T12:02:28Z

May 9, 2018 12:02pm

There are two issues, one code issue and one logic issue. Both of them has to do with how you define your return statements.

In C# all (non void) methods have to return a value. If C# detects that there is a possible scenario where a method will not return a value, then the code will not compile.

Now what will happen if your method is sent an empty list? The length of it will be 0, so your loop will never run. And since you don't have any return statements outside the loop, your method would not actually return anything. This is why your code does not compile.

The second issue is the logic of your conditional statement. Let's say I sent in a list that looks like this : [1, 2, 3, 3] the method should return true for that list, but your method would return false.

During the first iteration of the loop it would compare 1 and 2 and find that they are not equal, and then it would run the else statement which returns false. The return statement causes a method to return a value and then exit. So the loop never ends up continuing past that first iteration.

The solution to both of the those issues is to move the return false statement outside of the loop. Like this:

namespace Treehouse.CodeChallenges
{
    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {
            //use a for loop
            for(int i=0; i < sequence.Length; i++)
            {
                // comparing the actual value in the array with the previous one
                if (i > 0 && sequence[i] == sequence[i-1])
                {
                    return true;
                } 
            }
            return false;
        }
    }
}

That way your function will always return something. And when two numbers don't match the loop will simply continue to its next iteration. rather than returning right away.

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Tiago Ramos

Tiago Ramos

Am I acessing the values in the array correctly?

1 Answer

andren

andren

Tiago Ramos

Tiago Ramos