rev2023.3.3.43278. The basic strategy is to get the values from the HashMap in a list and sort the list. Originally posted by David O'Meara: Then when you initialise your Comparator, pass in the list used for ordering. For example, the following code creates a list of Student and in-place . Here, the sorted() method also follows the natural order, as imposed by the JVM. Learn more about Stack Overflow the company, and our products.
Sorting list based on values from another list - Stack Overflow If you have any suggestions for improvements, please let us know by clicking the report an issue button at the bottom of the tutorial. zip, sort by the second column, return the first column. I have two lists List
list1 = new ArrayList(), list2 = new ArrayList(); (Not the same size), of the class Person: I want to create a new list using list1 and list2 sorted by age (descending), but I also another condition that is better explained with an example: He should, because his age is equal to Menard, Alec is from L1 and two Person from L1 can't be one after another is this kind of situation happens. Find centralized, trusted content and collaborate around the technologies you use most. What is the shortest way of sorting X using values from Y to get the following output? The most obvious solution to me is to use the key keyword arg. There are a few of these built-in comparators that work with numbers (int, double, and long) - comparingInt(), comparingDouble(), and comparingLong(). You are using Python 3. Using Comparator. That way, I can sort any list in the same order as the source list. Using Java 8 Streams Let's start with two entity classes - Employee and Department: The . If we sort the Users, and two of them have the same age, they're now sorted by the order of insertion, not their natural order, based on their names. More general case (sort list Y by any key instead of the default order), http://scienceoss.com/sort-one-list-by-another-list/, How Intuit democratizes AI development across teams through reusability. Stop Googling Git commands and actually learn it! How can I pair socks from a pile efficiently? Sort a List of Objects by Field in Java - Hire Amir This is actually the proper way of doing it: when you sort a Factory, you cannot sort the inner competitors at the same time, because different objects are being compared. Note that you can shorten this to a one-liner if you care to: As Wenmin Mu and Jack Peng have pointed out, this assumes that the values in X are all distinct. Once you have that, define your own comparison function which compares values based on the indexes of list. :param lists: lists to be sorted :return: a tuple containing the sorted lists """ # Create the initially empty lists to later store the sorted items sorted_lists = tuple([] for _ in range(len(lists))) # Unpack the lists, sort them, zip them and iterate over them for t in sorted(zip(*lists)): # list items are now sorted based on the first list . In Java How to Sort One List Based on Another. Not the answer you're looking for? This is generally not a good idea: it means a client of Factory can modify its internal structure, which defeats the OOP principle. Unsubscribe at any time. Returning a negative number indicates that an element is lesser than another. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. But it should be: The list is ordered regarding the first element of the pairs, and the comprehension extracts the 'second' element of the pairs. Sign up for Infrastructure as a Newsletter. You can checkout more examples from our GitHub Repository. The Collections (Java Doc) class (part of the Java Collection Framework) provides a list of static methods which we can use when working with collections such as list, set and the like. This can be elegantly solved with guava's Ordering.explicit: The last version of Guava thas supports Java 6 is Guava 20.0: First create a map, with sortedItem.name to its first index in the list. P.S. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. So we pass User::getCreatedOn to sort by the createdOn field. Something like this? Something like this? How can I check before my flight that the cloud separation requirements in VFR flight rules are met? You posted your solution two times. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I think that the title of the original question is not accurate. You can create a pandas Series, using the primary list as data and the other list as index, and then just sort by the index: This is helpful when needing to order a smaller list to values in larger. Can I tell police to wait and call a lawyer when served with a search warrant? All Rights Reserved. Let's define a User class, which isn't Comparable and see how we can sort them in a List, using Stream.sorted(): In the first iteration of this example, let's say we want to sort our users by their age. We will also learn how to use our own Comparator implementation to sort a list of objects. Sign up for Infrastructure as a Newsletter. The solution here is not to make your class implements Comparator and define a custom comparator class, like. Once you have a list of sorted indices, a simple list comprehension will do the trick: Note that the sorted index list can also be gotten using numpy.argsort(). Disconnect between goals and daily tasksIs it me, or the industry? One with the specific order the lists should be in (listB) and the other has the list of items (listA). This gives you more direct control over how to sort the input, so you can get sorting stability by simply stating the specific key to sort by. Most of the solutions above are complicated and I think they will not work if the lists are of different lengths or do not contain the exact same items. @Richard: the keys are computed once before sorting; so the complexity is actually O(N^2). His title should have been 'How to sort a dictionary?'. Now it produces an iterable object. Sorting a Java list collection using Lambda expression Since Java 8 with Lambda expressions support, we can write a comparator in a more concise way as follows: 1 Comparator<Book> descPriceComp = (Book b1, Book b2) -> (int) (b2.getPrice () - b1.getPrice ()); 2) Does listA and listB contain references to the same objects, or just objects that are equivalent with equals()? This comparator sorts the list of values alphabetically. You can have an instance of the comparator (let's call it factoryPriceComparator) and use it like: Collections.sort (factoriesList, factoryPriceComparator);. Lets look at a quick example to sort a list of strings. Sorting a list based on another list's values - Java 16,973 Solution 1 Get rid of the two Lists. If the elements are not comparable, it throws java.lang.ClassCastException. The signature of the method is: The class of the objects compared by the comparator. will be problematic in the future. Here if the data type of Value is String, then we sort the list using a comparator. Java 8 Streams: Find Items From One List Based On Values From Another List Please mail your requirement at [emailprotected] Duration: 1 week to 2 week. Any suggestions? Oh, ignore, I can do sorted(zip(Index,X,Y,Z)) too. Sorting a 10000 items list 100 times improves speed 140 times (265 ms for the whole batch instead of 37 seconds) on my unit tests. Asking for help, clarification, or responding to other answers. Is there a solution to add special characters from software and how to do it. Finally, we've used a custom Comparator and defined custom sorting logic. This gives you more direct control over how to sort the input, so you can get sorting stability by simply stating the specific key to sort by. I can resort to the use of for constructs but I am curious if there is a shorter way. Application of Binary Tree. This method returns a lexicographic-order comparator with another comparator. Thanks for your answer, but I get: invalid method reference: "non-static method getAge() cannot be referenced from a static context" when I call interleaveSort. If you try your proposed code, it would give something like this: Person{name=Giant L2, age=100} Person{name=Derp L1, age=50} Person{name=John L2, age=50} Person{name=Menard L1, age=44} Person{name=Lili L1, age=44} Person{name=Lili L2, age=44} Person{name=Menard L2, age=44} Person{name=Bob L1, age=22} Person{name=Alec L1, age=21} Person{name=Herp L1, age=21} Person{name=Alec L2, age=21} Person{name=Herp L2, age=21} Person{name=Alice L1, age=12} Person{name=Little L2, age=5} And it's not what I'm looking for. Then we sort the list. Can you write oxidation states with negative Roman numerals? How to sort one list and re-sort another list keeping same relation python? All rights reserved. If we talk about the working of this method, then the method works on ASCII values. Linked List Operations: Traverse, Insert and Delete How do I split a list into equally-sized chunks? As you can see that we are using Collections.sort() method to sort the list of Strings. - the incident has nothing to do with me; can I use this this way? @RichieV I recommend using Quicksort or an in-place merge sort implementation. The Collections class has two methods for sorting a list: The sort() method sorts the list in ascending order, according to the natural ordering of its elements. As you can see from the output, the linked list elements are sorted in ascending order by the sort method. You can implement a custom Comparator to sort a list by multiple attributes. I was in a rush. As for won't work..that's right because he posted the wrong question in the title when he talked about lists. Starting with the example input you provided: This is also known as the Schwartzian_transform after R. Schwartz who popularized this pattern in Perl in the 90s: Note that in this case Y and X are sorted and compared lexicographically. Java Sort List Objects - Comparator Summary Collections class sort () method is used to sort a list in Java. The solution below is simple and should fix those issues: Location of index in list2 is tracked using cur_loclist. If the list is greater than or equal to 3 split list in two 0 to 2 and 3 to end of list. Speed improvement on JB Nizet's answer (from the suggestion he made himself). If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? In case of Strings, they're sorted lexicographically: If we wanted the newly sorted list saved, the same procedure as with the integers applies here: Check out our hands-on, practical guide to learning Git, with best-practices, industry-accepted standards, and included cheat sheet. Sort Elements of a Linked List. Getting key with maximum value in dictionary? i.e., it defines how two items in the list should be compared. How do you ensure that a red herring doesn't violate Chekhov's gun? good solution! Make the head as the current node and create another node index for later use. The common non-linear data structure known as a tree. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup, The most efficient way to merge two lists in Java, Java merge sort implementation efficiency. People will search this post looking to sort lists not dictionaries. Whats the grammar of "For those whose stories they are"? As for won't work..that's right because he posted the wrong question in the title when he talked about lists. more_itertools has a tool for sorting iterables in parallel: I actually came here looking to sort a list by a list where the values matched. 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