Finding the greatest sum of a pair of values from a 2d-array in Python

Question

I have a 2d-array with positive integers (limited to max. of 10^6). The array has a size of 10^5x2 like this:

140173 471588 291471 516770 273559 538464 125329 159490 5034   59284  438681 467752 578846 ...
80182  120937 410438 338171 169200 123061 175433 159358 462440 260476 179648 395141 508690 ...

Now, I need to find the biggest pair of values from the Array, with pairs formed by using one Value of the top row and one from the bottom row. I have a working python example, but it is really slow (attached below). How can I make this faster, or even better, is there a better way?

def solve(n, a, b):

    gD = int(0)

    for i in range(n):
        for j in range(n):
            d = (a[i] + b[j])
            if d > gD: gD = d

    return gD

n is the length of the two arrays, they're of equal length. I loop over every possible value, and if it is bigger than the prev. biggest pair, I save it in gD

Why are you not just adding the maximum value from the top row to the maximum value from the bottom row? — timgeb
– timgeb, Commented Sep 27, 2020 at 9:19
is a pair made of the values on the same column ? Or can it be, for example, value of 1st row column 5 and value of 2nd row column 10 ? — ValLeNain
– ValLeNain, Commented Sep 27, 2020 at 9:36
@timgeb I am fairly new to python and didn't know this existed, but I also need the index of the max value — jesseb0rn
– jesseb0rn, Commented Sep 27, 2020 at 10:34

Ruli · Accepted Answer · 2020-09-27 10:36:17Z

1

Maybe just use max?:

list1 = [44545,8876,4571]
list2 = [46321,8468,77798]

print(max(list1)+max(list2))
#122343

to return the first occurrence (there can be multiple elements of same value) of max value:

id = list1.index(max(list1)) #0
id2 = list2.index(max(list2)) #2

edited Sep 27, 2020 at 10:36

answered Sep 27, 2020 at 9:22

Ruli

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3 Comments

jesseb0rn Over a year ago

Is it possible to get the index of the max value with this?

Ruli Over a year ago

@jesseb0rn I have edited the code to get ids of first or second list

jesseb0rn Over a year ago

@Ruli Thank you for the quick answer! Helped a lot!

dimay · Accepted Answer · 2020-09-27 09:18:22Z

0

Try this:

max(i+j for i in a for j in b)

answered Sep 27, 2020 at 9:18

dimay

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Comments

Gaëtan de Menten · Accepted Answer · 2021-01-15 09:33:47Z

0

Using max seems like the easiest solution.

To mimic your own "solve" function, you could use something like:

def solve(n, a, b):
    assert len(a) == n and len(b) == n
    return max(a) + max(b)

But I wonder if passing n is worth it. If that is not a requirement, you would get:

def solve(a, b):
    assert len(a) == len(b)
    return max(a) + max(b)

edited Jan 15, 2021 at 9:33

answered Sep 27, 2020 at 9:31

Gaëtan de Menten

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