Interview question: Integer index question

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I was asked about this question in interview:
Integers in an array are unique and increasingly sorted. Write a function to find an integer from the array who equals to its index. E.g. in the array {-3, -1, 1, 3, 5}, the number 3 equals its index 3.

Any ideas?

Posted 28-Sep-15 17:22pm

jakecook

Updated 28-Sep-15 17:58pm

PIEBALDconsult

v2

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PIEBALDconsult 28-Sep-15 23:59pm

Zero-based or one-based indices?
Every member of the array equals its index if you provide the right base.

CPallini 29-Sep-15 3:21am

That's pretty trivial. What is your doubt about?

2 solutions

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Hank Williams · Answer 1 · 2015-09-28T17:53:00

VB

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        
        Dim numbers = New Integer() {-3, -1, 1, 3, 5}


        MsgBox(Find_Index_Value_Same_As_Array_Value(numbers))



    End Sub

    Private Function Find_Index_Value_Same_As_Array_Value(ByVal _Array() As Integer) As Integer



        Find_Index_Value_Same_As_Array_Value = -1




        '--- Find The Max Number For The Array Index

        Dim _Max As Integer = UBound(_Array)

        Dim _My_Counter As Integer = 0

        For _My_Counter = 0 To _Max
            If _My_Counter = _Array(_My_Counter) Then
                Find_Index_Value_Same_As_Array_Value = _Array(_My_Counter)
                Exit Function
            End If
        Next

        

    End Function

George Swan · Answer 2 · 2015-09-28T20:26:00

Solution 2

C#

int[] numbers = { -3, -1, 1, 3, 5 };

int[] results = numbers.Where((nbr, i) => i == nbr).ToArray();
string message = results.Length == 0
? "Nothing found"
: string.Format("Found {0}. First is at index {1}", results.Length, results[0]);
          Console.WriteLine(message);

Posted 28-Sep-15 20:26pm

George Swan