Problem 661. Spot the outlier

Created by Ned Gulley

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All points except for one lie on a line. Which one is the outlier?
Example:
You are given a list of x-y pairs in a column like this:
 pts = [ 0 1 
         0 2 
         3 2
         0 3 
         0 4 ]
You would return the number 3, since the third point is the only one that is non-collinear with the other points. All the others are on the y-axis.
 outlier = 3
 

Solve

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Last Solution submitted on Nov 02, 2025

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3 Comments

Justin on 29 Apr 2014

The instructions were a bit confusing at first. It would have been better to say "Find the row number of the outlying point."

Also, using the third row as an answer and a 3 in a column of zeros makes it seem like the intent was to provide unclear instructions. (Or they are just used to writing college textbooks ;) )

Wenwu on 8 Jan 2015

The test set cases 2,3 seems to have two outliers for each case. Please check it

Josh on 10 Aug 2023

i struggled with this one, not so much because of the concepts/maths involved, but because of issues with floating point precision that occur with test case 3 where my functions kept erroring after determining that 15.0000 ~= 15

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Problem 661. Spot the outlier

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