//Today's Challenge // triangle number in a list or array

Question

Given a list/array of numbers try to identify the numbers in the list whose previous number is their triangle number

Triangle no eg. If n is a triangle number of x then 1+2+3+... +(n-1)+(n)=x

Eg.
List = [4,5,3,6,7,28]

Output = [6,28]

Since 3 and 7 are there triangle numbers

Answer 1

Thank you for the challenge.
Here's my try :
https://code.sololearn.com/cbGNKV5h4wIU/?ref=app

Answer 2

My try:
https://code.sololearn.com/c6E2uAP7jfTL

Answer 3

My try
https://code.sololearn.com/coGIaf6EN5aZ/?ref=app

Answer 4

💟💟🎉🎉🎉
finally, all is done,, Here is the full solution with printed results too.
https://code.sololearn.com/WyOG7vaxzWLG/?ref=app

Answer 5

Tried with functional programming.
Would never do it again.

https://code.sololearn.com/cL6Uy6H47e3H/?ref=app