kreznykov It should have a super easy difficulty.
mubparekh Please share your approach
[deleted] struct Player { string name; int score; }; bool comp(Player p1, Player p2){ if(p1.score>p2.score) return true; if(p1.score==p2.score) return p1.name<p2.name; return false; } vector<Player> comparator(vector<Player> players) { sort(players.begin(),players.end(), comp); return players; }
JChiquin You can simplify the function
compif you convert it into this:bool comp(Player &A, Player &B){ return A.score==B.score and A.name<B.name or A.score>B.score; }
Also and just for fun, it can use a lambda expression in its place:
vector<Player> comparator(vector<Player> players) { sort(players.begin(),players.end(),[](Player &A,Player &B){return A.score==B.score and A.name<B.name or A.score>B.score;}); return players; }
malika_messaoud1 In case of equality i think we have some checks and swaps to do according to specification of question , my code , sorry i don't know how to display ut in better way :
comparator(player A,Player B) {
if(A.score > B.score) return 1; else if(A.score < B.score) return -1; else if(A.score == B.score) sortChars(A.name,B.name); return 0; }
void sortChars(string s1,string s2){
string shorter = s1 < s2 ? s1 : s2;
for(int i =0; i val2){ s1.swap(s2); return; } else { if(val2 > val1) return; } else continue; }
if (shorter == s1) s1.swap(s2); else return; }
AnushaGhosh why cant we directly return 0 instead of p1.name
Matthewpdias just for fun with ternary
bool compare(const Player& p1,const Player& p2) { return p1.score > p2.score ? true : (p1.score == p2.score ? p1.name < p2.name : false); } vector<Player> comparator(vector<Player> players) { sort(players.begin(), players.end(), compare); return players; }
KeerthiRaj850 return (a.score==b.score)?(a.name.compareTo(b.name)):Integer.valueOf(b.score).compareTo(Integer.valueOf(a.score));
dhingra_ankush05 Simpler way in java.
class Checker implements Comparator<Player> { public int compare(Player a, Player b){ if(a.score>b.score) return -1; else if(a.score<b.score) return 1; else return a.name.compareTo(b.name); } }
raduri Absolutely. If this is "Medium", wonder what "Easy" could look like :P.
muthangyamusyoka Write a function that prints "Hello world!" in your language of choice.
bingli224 println ( "Hello world!" )
Is this what you mean?
muthangyamusyoka Exactly ;)
Paul_Denton Agree if you just implement the comparator thingy and use sort from the standard lib.
aarduain That defeats the purpose completely.
vataseluandrei1 It's super easy without any comparator thingy in Python
def comparator(a, b): if a.score > b.score: return -1 elif a.score < b.score: return 1 elif a.score == b.score: if a.name > b.name: return 1 elif a.name < b.name: return -1 else: return 0
profnandaa This should do too:
def comparator(a, b): if a.score > b.score: return -1 elif a.score < b.score: return 1 elif a.name > b.name: return 1 return -1
M_F_H This returns -1 in case of equality. Although it might yield the correct result for the sorted list, it is not conforming to the specification. It may give wrong result if used to test equality when searching an object in the sorted list. It may also lead to additional swaps in the sorting process.
malika_messaoud1 M_F_H thank you i was wondering i was the only to think about swapping in case of equality
gauravkrsingh849 definitly
CarlinS Note that all the elses are unecesary since you're exiting the function at each if statement. Mine was:
if a.score > b.score: return -1 if a.score < b.score: return 1 if a.name > b.name: return 1 if a.name < b.name: return -1 return 0
c_m_s_gan I thought I had to manipulate the bubble sort algo somehow, until I discovered how this comparator thingy works.
spriyadharshini4 can anyone tell me how this code works?
shashankraj07 Would you please explain the 1 and -1 concept. I am beginer to python. Thanks in advance!!
andikadevs The resource is Quicksort video. Then I see sample comparator code then I use it and not using Quicksort. Lol...
aarduain Really guys? Come on, this isn't easy for everyone
tatianaensslin definitely depends on the langage youre using, i suppose
PavelKK It shouldn't be there at all.
bingli224 but unless with unfamiliar languageisabelladom247 The details always help me to understand specific topic details. The details are helping to understand the topic in every direction hostsailor . That creates a better understanding of the thing. The detailed description along with the proper example make things very clear.
gussy In Python 3, I think the template code is incorrect. We can solve it by writing this
def comparator(a, b): if a.score < b.score: return 1 if a.score > b.score: return -1 if a.name < b.name: return -1 if a.name > b.name: return 1 return 0
However if the line
data = sorted(data, key=cmp_to_key(Player.comparator))
was changed to
data = sorted(data, key=Player.key)
we could solve it with the better
def key(self): return(-self.score, self.name)
We can use the second approach by dummying out the cmp_to_key function.
def cmp_to_key(key): return key class Player: def __init__(self, name, score): self.name = name self.score = score def comparator(self): return(-self.score, self.name)
jaj_jaj if in other place you will need to sort players using different criteria, will you change class Player again?
fisher6 You, my friend, are a true hacker.
taoyu_forever for the code: if a.name < b.name: return -1
why here return -1, but not 1?
M_F_H -1 means "a comes before b", which is what we want if score is equal and name of 'a' is < name of 'b'.
morita657 cmp_to_key function is nice idea! I have learnt new thing from yours! Thank you!
nacho2 Hi gussy, as documentation says, Python 3 no longer supports comparer functions for classes, it uses a tool function to map between old comparer (that i think HackerRank is used to put in their excercises) and Python 3 comparers:
"functools.cmp_to_key(func) Transform an old-style comparison function to a key function. Used with tools that accept key functions (such as sorted(), min(), max(), heapq.nlargest(), heapq.nsmallest(), itertools.groupby()). This function is primarily used as a transition tool for programs being converted to Python 3 where comparison functions are no longer supported.
A comparison function is any callable that accept two arguments, compares them, and returns a negative number for less-than, zero for equality, or a positive number for greater-than. A key function is a callable that accepts one argument and returns another value to be used as the sort key."
So it takes a func and turns that into something that Python 3 understands.
Source: link
sachin4u4u can anyone explain what is differnce between return 1, return 0 and return -1
nacho2 -1 = a < b
0 = a == b
1 = a > b
a comparer need to tell you if a number is equal, grater or lower than other number, thats why you have 3 possible outputa
artbindu wow your comparator function work wonderful.
i did not understand about your function: ''' def comparator(a, b): if a.score < b.score: return 1 if a.score > b.score: return -1 if a.name < b.name: return -1 if a.name > b.name: return 1 return 0 ''' can you send me any link to understand it well
iunir_iakupov Hi, I solved it in Python 3 without changing anything outside Player class:
def comparator(a, b): if a.score != b.score: return b.score - a.score return (a.name>b.name)-(a.name<b.name)And I agree template is incorrect. We don't need to implement repr
phuocnguyenbk15 Why do we use variable a,b in comparator function? a,b has attributes: name and score when we define the class, right?
gul357 "data" is list (of objects created from class Player).
For sorting the elements in data (based on attributes "score" & "name"), we are comparing 2 objects at a time (using the comparator() method of class Player). Its very similar to the concept when two items are being compared in Bubble sort or Quick sort.
Hope it helps.
jimmyxbw Simple Java implementation:
class Checker implements Comparator<Player> { @Override public int compare(Player a, Player b) { if(a.score != b.score) { return b.score - a.score; } return a.name.compareTo(b.name); } }
shweta78 could you please explain this?
tylerFowler Subtracting the two scores will either give a negative (indicating less than) or positive (indicating greater then) number. Roughly equivalent to the standard:
if (b.score < a.score) return -1; if (b.score > a.score) return 1;
solidwater Hi Team,
Can you also enable C# in editor for this problem
FaxMachin3 Thank God I remembered some Python and Java.
aaron_newton JavaScript would be nice too.
jarb2104 I would love this to, had to go with C++
samirbaaz class Player: def __init__(self, name, score): self.name = name self.score = score def __repr__(self): pass def comparator(a, b): val = b.score - a.score if val == 0: return -1 if a.name < b.name else 1 return val
nik_roby I ended up with nearly identical structure.
erdenezul def comparator(a, b): name_score = int(b.name > a.name) return b.score - a.score - name_score
dimple97verma Please help me in understanding the comaparator method.How is it taking 2 objects of the class Player as argument?Also i am unable to understand the logic in the statements of comparator method.
riteshk615 from functools import cmp_to_key class Player: def init(self, name, score): self.name=name self.score=score def repr(self): pass
def comparator(a, b): if a.score < b.score: return 1 if a.score > b.score: return -1 if a.name < b.name: return -1 if a.name > b.name: return 1 return 0n = int(input()) data = [] for i in range(n): name, score = input().split() score = int(score) player = Player(name, score) data.append(player)
data = sorted(data, key=cmp_to_key(Player.comparator)) for i in data: print(i.name, i.score)
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