Recursion in python need help understanding

Question

i need help understanding this recursion thing
i am new to coding and trying to learn python

def tri_recursion(k):
    if(k > 0):
        result = k + tri_recursion(k - 1)
        print(result)
    else:
        result = 0
    return result

print("nnRecursion Example Results")
tri_recursion(6)
 
Recursion Example Results
1
3
6
10
15
21

i understood 1 and 3
i never understand why the answer is 6 by the third row
because
result = 3 + tri_recursion(3-1)
print(result) which is 5 right ?

Asked By: MarkJayForCode

||

Source

Answer 1

It may help to print out k with your result

def tri_recursion(k):
    if(k > 0):
        result = k + tri_recursion(k - 1)
        print(f"k: {k} = {result}")
    else:
        result = 0
    return result

print("nnRecursion Example Results")
tri_recursion(6)

produces

Recursion Example Results
k: 1 = 1
k: 2 = 3
k: 3 = 6
k: 4 = 10
k: 5 = 15
k: 6 = 21

So you can see for each k that it is itself + the result from the previous line.

Answered By: saquintes

Answer 2

Here’s how it works:

tri_recursion(1): result = k = 1

tri_recursion(2): result = k + tri_recursion(2-1) = k + tri_recursion(1) = 2 + 1 = 3

tri_recursion(3): result = k + tri_recursion(3-1) = k + tri_recursion(2) = 3 + 3 = 6

… and so on

Hope it helps!

Answered By: elnoidelfarro

Recursion in python need help understanding

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