CODEWITHSUNDEEP
pythonlistloopssyntax
Willy Gorfman
Willy Gorfman

Reputation: 3

(Syntax) Getting the index of the biggest difference between two lists (in 1 line)

I know this can easily be done in a for loop, but I'm thinking there must be an intuitive way to do this in 1 line. For more explanation - you are given two lists, "juice" and "capacity". juice shows how much juice a certain index has and capacity shows the capacity of the index. I'm trying to find the index with the most remaining capacity. So I tried to do that by doing this:

maxCap = max(capacity[i] - juice[i] for i in range (0, N - 1))

But of course this doesn't save the index. How can I assign maxCap to the "i" which produces the maxCap as I have written?

Upvotes: 0

Views: 39

Answers (2)

sardok
sardok

Reputation: 1116

You may use reduce:

import functools
remainings = [capacity[i] - juice[i] for i in range (0, len(capacity) - 1)]
maxCap = functools.reduce(lambda acc, cur: acc if remainings[acc] > remainings[cur] else cur, range(len(remainings)), 0)

Reduce iterates over the iterable and returns a single result determined by the given reducer function.

Upvotes: 0

zvone
zvone

Reputation: 19352

maxCap = max(capacity[i] - juice[i] for i in range (0, N - 1))

This same thing can be done simpler this way (although I don't understand the N-1 part, so I am ignoring it):

maxCap = max(c - j for c, j in zip(capacity, juice))

Still, that gives the result, not the index. To find the index, max has to go through i values, rather than the calculated results, but maximise the results, like this:

max_index = max(range(N), key=lambda i: capacity[i] - juice[i])

On the other hand, if you are looking for efficiency, this is a good thing for numpy. If both juice and capacity are numpy arrays, then this can be done:

max_diff = (a - b).max()
max_index = (a - b).argmax()

Upvotes: 1

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