Viewed 2k times. I tried to create my own: using System. Collections; using System. Generic; namespace Collections. I omit its code for brevity That would allow code to branch based on the success of the Add T item method like so: if orderedSet. Add foo ; if orderedSet. Improve this question. I'll add comments tomorrow I'll add comments tomorrow 2, 8 8 silver badges 19 19 bronze badges.
It's often impractical to fulfill it's entire contract. Make a practical decision. API users likely want to use your class as an IList so give it to them and document where the abstraction leaks. Add a comment. Sorted by: Reset to default.
Highest score default Date modified newest first Date created oldest first. Improve this answer. MattPutnam MattPutnam 2 2 silver badges 3 3 bronze badges. In my eyes definitely YES! Some of the IList members doesn't make sense in combinations with a set. That is not the behavior that i would expect from an object of type IList. Attempting any such operation should never cause an exception. Let's take e. In addition, by making these variables readonly your code will become more robust.
Heslacher Heslacher Instead of checking the input, I could also just try to make the call and then re-throw any occurring exception in a non-leaking way. Is that a worse solution? Throwing the exception in a non leaking way would mean loosing the stacktrace. You should consider this option only if you have a possibility to first log the inital exception including the stacktrace.
Remove item? Peter Taylor Peter Taylor AddRange items ; Assert. AreEqual 7, list. Count ; CollectionAssert. AddRange items2 ; CollectionAssert. Remove 3 ; Assert. Remove 1 ; Assert. IsTrue removed ; Assert. AreEqual 5, list. Remove 9 ; Assert. Remove 11 ; Assert. IsFalse removed ; Assert. Coda Coda 81 3 3 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. For every number, you need to find the count of numbers coming before it and having value greater than it.
If you have a data structure which stores elements in sorted order then while inserting any element in it you can check how many elements already exist in it whose value is greater than this element. We have already inserted elements upto this index. We want inversions formed with this index. Similarly this is done for each index from 0 to n So if we can find the position pos of an element in the data structure, we can easily solve this problem.
We know that set and multiset store elements in sorted order. But they dont provide any function to find to find position of an element, They can just provide the value of element. Therefore we can't use them for such situation. But Ordered Set comes to our rescue. Note : To handle duplicate elements in the above code perform changes as discussed in the section. Type 1 : insert k : Insert an element. Type 2 : findKthSmallest k : Return kth smallest element. Time complexity : O log n.
But we may not always have all unique elements. Therefore we want same functionality with multiset also. Now use second value in pair as unique for every value take as index in original array. The first value in pair is the actual value of the element. Now each pair element will be unique and we are also able to store duplicate elements by storing their indexes.
Codeforces Problem D. Nested Segments. Thank you for your patience reading. I am a Member Technical at D. Shaw India Pvt. CodingWithArt is a blog where you find tricks and solutions to challenging coding and development problems.
After a relatively long lull, I decided that my contribution growing too slowly the hour has come to please you with another article in the blog :. Some time after I tested it on various tasks and, unfortunately, tend to get a negative result — rope was too slow, especially when it came to working with individual elements. For some time, I forgot about that article. Increasingly, however, I was faced with problems in which it was necessary to implement set with the ability to know ordinal number of item and also to get item by its ordinal number ie, order statistic in the set.
And here begins my fascinating acquaintance with policy based data structures, and I want to tell you about them :. Let's get started. In this article I will talk about IMO the most interesting of the implemented structures — tree. We need to include the following headers:. Experienced participants may have already noticed that if initialize the template only the first two types, we obtain almost exact copy of the container map.
Let us examine them in more detail. Tag — class denoting a tree structure, which we will use. Sadly, at competitions we can use only red-black trees for this because splay tree and OV-tree using linear-timed split operation that prevents us to use them. Consider them. Most likely, the best way to set the tree is as follows:. If we want to get map but not the set, as the second argument type must be used mapped type.
The first returns an iterator to the k-th largest element counting from zero , the second — the number of items in a set that are strictly smaller than our item. Example of use:. For this, I provide the following table. At the same time the code size is reduced considerably.
Besides tree, I also wanted to describe here trie. However , I was confused by some aspects of its implementation, greatly limiting its usefulness in programming olympiads, so I decided not to talk about it. If anyone want he is encouraged to try to learn more about this structure by himself.
Example of trie with search of prefix range. Is there a way of counting number of strings in the trie with a certain prefix without iterating through them all? You augment the trie node to also contain a number. Update this number everytime you insert a string into the trie. To get the number of strings which share the prefix, Just traverse the prefix and output the num in the ending node. Most likely, later I'll provide an entry about some interesting ways of using this structures, which are quite rare.
As I know, there is no implemented tree multiset in STL. Apparently, you can. But it works incorrectly. This code erase 1, not 0. Seems like I only used it with insert operations and strangely enough it worked. Well, actually it works fine and exactly does what you want! Thus returns the first element greater than val which is 1 in your example. Can we use this in this question?
But adamant , is it the correct way to do this? Since as far as I know, most of the STL containers require a comparator that offers a strict weak ordering Not sure of the exact reasons though. So, will there be some drawbacks of trying to construct a multiset this way?
I mean that's not right to do but will get u AC i think :p. It also gives 2 more features: find the Kth element and find the rank of the Xth element. The problem is that this doesn't allow duplicates :. No Worries though! I've attached my implementation below for reference. Also, let's say you want to erase x, use s. This is actually great. This is much simpler. You can do in log n if the greatest element of 1 tree is smaller than smallest of other. Otherwise, I don't you have a better option.
Tell me as well if you have found something interesting. How do you merge two non-intersected rbtrees as in the article in O lg n time? I find that the default join function takes linear time Hi, adamant , the code files in Useful Links don't seem to work. Could you fix them? For example, the code in "Demonstration of trie with prefix search" cannot run on my computer.
I changed it, then it returned a new error in another place. The truth is I am not good enough to change things any more. I hope that you can update it. I know that I can use the trie code in one of your comments, but this post would be even better if the cost in Useful Links were also updated. I can't edit the original files — they're not mine. Can anybody share a Java equivalent class for this type of set or a code which acts according to above data structure? I want to handle online queries.
But here again is the problem of implementation of mixed data structure, I am unable to think how to implement that. Can you please help me? How can I use a custom compare function in the "Key comparison functor" section for custom data types? I can use custom compare function for a set by using operator overloading.
I want to know is there any other way to do this for both set and ordered set using lambda expression or just using a compare bool function? Also you can use functors and lambdas in the way similar as for sets:. How To Solve This Problems. Plz Help Me. I sometimes find myself have to use my own tree templates instead because of having to write a search function that can cope with this task.
I think it's constant factor is very high. So I tried to do that by couldn't. It gives an error. It says no known conversion. What exactly do you expect it to return?.. I have been searching for that for a long time. Can u please provide us with a multiset implementation.
And I believe this would be useful to a lot of coders. You can try this to erase by value from ordered multiset or wwhatever it's called in technical terms. To erase by value from Ordered Multiset: os. For me, I installed the latest version of gcc gcc 9. I wasn't aware that this was the root of the issue and had been missing pbds structures for a long time. Note In the example, the duplicate element "perls" is only present once in the SortedSet.
C program that uses SortedSet constructor. Sometimes you may need to remove all elements from your SortedSet that match a certain condition. You can invoke the RemoveWhere method. Here In this example, four names are added to the SortedSet that start with the letter s. Then We call RemoveWhere with a lambda that is used as a predicate condition. When the method returns true, the element is removed. Add method. We call the Add method to put additional elements into the set.
The Add method returns a boolean value that tells us whether or not a new element was added. Result If it returns true, a new element was added. If it returns false, the element already existed in the set and was not added again. Count, clear. As with other collections, you can use the Count property and the Clear method on the SortedSet type. Please notice that the Count property can only be read, not assigned to.
Tip After the Clear method is called, the Count property will always return zero. This returns the union of two collections. Result The UnionWith method adds all the elements into one collection. No duplicates will be found in the SortedSet.
This returns all elements that are found in only one collection. You do not need to copy the variable reference. This removes all elements found in a collection from the SortedSet. The resulting SortedSet will contain all its elements except those that were found in the other collection.
This tells us whether a collection has any elements in common with the SortedSet. Even if only one element is found in common, the result is True. Otherwise the result is False. This changes the set instance so that it contains only the elements that were present in both collections. The element count is reduced or stays the same. C program that calls IntersectWith method. Min, max. The SortedSet contains elements that are stored in ascending sorted order.
So it is trivial for the set to compute its lowest and highest values. Also You cannot use an indexer with the SortedSet, so these properties are useful. C program that demonstrates Min and Max properties. Subsets, supersets. SortedSet has methods to compute subsets and supersets. Definitions A subset is contained entirely inside another set. A superset contains entirely another set. Note Proper subsets and supersets cannot have the same number of elements.
They must have at least one fewer. This tells us if 2 collections have the same elements.
std::set is an associative container that contains a sorted set of unique objects of type Key. Sorting is done using the key comparison. Ordered set is a policy based data structure in g++ that keeps the unique elements in sorted order. It performs all the operations as performed. We need ordered data. · We would have to print/access the data (in sorted order). · We need predecessor/successor of elements. · Since set is.