iwc
A Common-Sense Guide to Data Structures and Algorithms, Second Edition: number_of_paths implementations are not equivalent (pg. 176/177)
There are two provided implementations for the number_of_paths function. The ‘hardcoded’ version is correct, but the simplified version is not.
pg. 176
def number_of_paths(n):
return 0 if n <= 0
return 1 if n == 1
return 2 if n == 2
return 4 if n == 3
return number_of_paths(n - 1) + number_of_paths(n - 2) + number_of_paths(n - 3)
end
pg. 177
def number_of_paths(n):
return 0 if n < 0
return 1 if n == 1 || n == 0
return number_of_paths(n - 1) + number_of_paths(n - 2) + number_of_paths(n - 3)
end
Page 177’s implementation returns 1 instead of 0 for number_of_paths(0).
First Post!
jaywengrow
Thanks for submitting this. While you are correct that the two methods are not identical in this regard, that is by design. I explain there in the text between the two versions that in the simplified version, we are “rigging” the base case of 0 to return 1 for the very sake of simplifying the code. I hope that helps!
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