def Triangular(n):
arr = []
for i in range(n):
T = i*(i+1)/2
arr.append(T)
if n == any(arr):
return True
else:
return False
All test cases are in False. Please show me what I was wrong
-
what are the test cases?n1c9– n1c92016-04-13 03:57:52 +00:00Commented Apr 13, 2016 at 3:57
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2 Answers
Try this lambda:
Triangular = lambda x: (0.5 * ((8 * x + 1) ** 0.5 - 1)).is_integer()
Here's how it works:
- Multiply
nby 8 and subtract 1 - Find the square root of that number
- Subtract it by 1 and divide it by 2
- Remove the decimal part of the number
- If the resulting number is greater than 0, it is triangular
You can also use this lambda from this answer to check if the number is Triangular:
Triangular = lambda n:(8*n+1)**.5%1>0
1 Comment
alexpghayes
As a one liner
is_triangular = lambda x: (0.5 * ((8 * x + 1) ** 0.5 - 1)).is_integer()any() returns a boolean, True or False. you are comparing it to n, an integer. Change the line to
if n in arr:
Or even better yet you can just delete the whole if..else statement and replace it with simply:
return n in arr
edit: you can even avoid creating an array in the first place like this:
def Triangular(n):
arr = []
for i in range(n):
if i*(i+1)/2 == n:
return True
return False
This immediately returns True when it finds that n is triangular. If it gets to the end of the list and doesn't find any, it returns false.
3 Comments
Xèo
Thanks for your answer.
ravi tanwar
what is the time complexity for this solution ?
Marcel Wilson
This fails on
1 which technically is triangular.