Challenge: Arithmetic Sequence
Find the index of an outlier in an arithmetic sequence.
Task
This task requires you to find the index of the first outlier in a given array. All numbers in an array are in an arithmetic sequence except one.
Write a program that uses an array and finds the index of the first outlier and stores it to the variable idx
. The array is guaranteed to have at least $5$ elements and the first two elements will be in the required arithmetic sequence. The value of the idx
should be $−1$ if the array has no outlier, and should be $0$ if the array length is less than $5$.
Sample input 1
array1 = [5,8,11,13,17]
The resulting value 1
index = 3
Expected output 1
The outlier value is at the index: 3
Sample input 2
array1 = [1,6,11,16,20]
The resulting value 2
index = 4
Expected output 2
The outlier value is at the index: 4
Sample input 3
array1 = [1,6,11]
The resulting value 3
index = 0
Expected output 3
The outlier value cannot be found.
Sample input 4
array1 = [2,4,6,8,10]
The resulting value 4
index = 1
Expected output 4
There is no outlier in the array.
How to test your program
When you click the “Test” button of the code widget, you get two options as explained below:

Show Results: It shows the sample inputs and their respective results in comparison with the expected output. The actual output is the outlier index calculated to display the results. The word “Succeeded” in the last column indicates that the calculated output matches the expected output. For example, if
array1
is[5,8,11,13,17]
and theidx
is3
, then the last column shows “Succeeded”. Similarly, ifarray1
is[2,4,6,8,10]
and theidx
is1
, then the last column shows “Succeeded”. 
Show Console: It shows the output from the
print()
statements used in your code. You may use this to verify your calculations on the basis of sample test inputs. For example, ifarray1
is[5,8,11,13,17]
, then the output on the console should beThe outlier value is at the index: 3.
. Similarly, ifarray1
is[2,4,6,8,10]
, then the output on the console should beThere is no outlier in the array.
.
# Assume that the following variable is already defined:# array1# You are required to use the above variables to find# the index of the first outlier in the array.# You may start your code from here to store the correct result in# the variable indexidx = 1