Largest Number - Leetcode 179 - Python 

Can just check first value of string too, concatenatedString[0] == '0' ? "0" : concatenatedString

Thank you!!!

@@shrimpo6416 WC Bro

nums = [str(num) for num in nums]

@@leeroymlg4692 This is what I did too!

lol... worked since Python has auto big number handling. return ''.join(nums).lstrip('0') or '0'

The way cmp_to_key function works is that you pass it a method (compare) that will either return -1, 1, or 0 in order to sort the items in the list. You don't actually need to return the values themselves because it just has to compare them to know which item is less or greater, then it will automatically sort the items.

@@FCBarcelonaXMI Thanks! That makes sense!

@@FCBarcelonaXMI My doubt is why we should return -1 for n1 going first ??

@@navamshuram I don't know if there is a particular reason why, that is just the way cmp_to_key function is designed to work in Python.

@@navamshuram I think this function sorted the return value. If the return value is -1 then it goes first.

That's definitely true, python makes it work but in other languages it probably won't work.

We can avoid that, just check if the sorted arrays first element is "0". if so, that means everything after it will also be "0" so we can just return "0" right there :) And if that is not good enough, we can sum the initial array, if it is 0, return "0". But that decreases the efficiency of the code.

@@nandhakiran6523 Great! It's clear and does not dependent on programming language.

Nums=list(map(str,nums))

Hey, my guess is as good as any but I was playing around with it. We're trying to compare elements, e.g. if we have a='30' and b='3' (in python notation), we are trying to figure out if a+b ('303') is larger than b+a ('330'). The cmp_to_key function is part of the functools module, and tells the sorting to use our comparison method. So if we want to decide whether to put '30' or '3' first, we look at whether a+b or b+a is bigger. In order to tell the key which is better, in almost a boolean sense, we say positive means change/don't change order, and negative means don't change/change order. So if we get in a='30' and b='3', (note that in the key function, the first value is later, so we would have a list that had [......, 3, 30, .......] in there, if a+b > b+a (303 > 330, not true in this case), we would pass a -1 (red flag), and the key function would switch order to have [...., 30, 3, .....]. In real life, that case wouldn't be true, and the key function would receive a 1 (green flag) so that it wouldn't have to switch the two. Bit long, but it's an odd question. Can't imagine answering this in an interview. Also note that you could return any positive/negative (e.g. 420/-69), but you can't return a 0 or it gets screwy. The delineator is positive vs negative as switch position after comparison vs don't switch position after comparison.

1. This key is eventually helping sorted() to arrange elements in ascending order; 2. It returns a negative value indicating the first argument is lesser than the second argument or a positive value indicating the first argument is greater than the second argument. So if n1 + n2 > n2 + n1 we want to put n1 first so we must tell it that n1 is the smaller one thus return -1

9 + 34 == 34 + 9

it doesn't compare numbers individually , it compares after concatenating them.

Actually you are supposed to preserve the order of the numbers so technically the answer you have for question 2 is incorrect 😕