22 questions linked to/from (When) is hash table lookup O(1)?
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### Why isn't an edge-map graph implementation used in practice?

Wikipedia states that three different graph implementations are used in practice: Adjacency Lists Adjacency Matrix Incidence Matrix While I was learning about these structures, another option ...
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### How does a hash table not require all the keys to be looked through to find a value, i.e. O(N)?

Before starting, I want to say that I understand time complexity, and I understand how a hash table is considered O(1) vs an array having a time comp. of O(N) in terms of what you learn. What I don't ...
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### "For small values of n, O(n) can be treated as if it's O(1)"

I've heard several times that for sufficiently small values of n, O(n) can be thought about/treated as if it's O(1). Example: The motivation for doing so is based on the incorrect idea that O(1) is ...
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### Time complexity of Hash table lookup

Suppose I have a hash table which stores the some strings. Let the index/key of this hash table be the length of the string. what is the time complexity of checking if the string of length K exists in ...
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### Simple Uniform Hashing Assumption and worst-case complexity for hash tables

Is the Simple Uniform Hashing Assumption (SUHA) sufficient to show that the worst-case time complexity of hash table lookups is O(1)? It says in the Wikipedia article that this assumption implies ...
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### What is the average search complexity of perfect hashing?

The lookup time in perfect hash-tables is $O(1)$ in the worst case. Does that simply mean that the average should be $\leq O(1)$?
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### is hash table a magic?

I have no cs background (algorithm and data structure), but need to find a data analysis related job since my major is math / statistics. However, (I am trying to avoid software engineering related ...
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### Best data structure for a queue with random reads?

Well, it's not exactly a queue if it allows for random reads. This question is about a data structure which behaves like a queue for insertions and a sorted dictionary for reads. Imagine an algorithm ...
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### Average number of collisions before successful insertion into hash table

I want to compute the average number of collisions before sucessfully adding an item into a hash table. Let $m$ be the size of a hash table $H$. I was thinking that since it is a linear probing and ...
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### How are hash tables O(1) taking into account hashing speed?

Hash tables are said to be amortized $\Theta(1)$ using say simple chaining and doubling at a certain capacity. However, this assumes the lengths of the elements are constant. Computing the hash of an ...
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### Can element uniqueness be solved in deterministic linear time?

Consider the following problem: Input: lists $X,Y$ of integers Goal: determine whether there exists an integer $x$ that is in both lists. Suppose both lists $X,Y$ are of size $n$. Is there a ...
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### Does my simple, static hash table have O(1) worst case lookup?

Will the following simple hash table construction algorithm be able to construct a static hash table in $O(n)$ expected time, and will the worst case access time be $O(1)$? If not, what are the ...
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### Hash table collisions: why use a linked list if we can use a hash set?

One way to deal with the problem of collisions for a hash table is to have a linked list for each bucket. But then the lookup time is no longer constant. Why not use a hash set instead of a linked ...
From the answers to (When) is hash table lookup O(1)?, I gather that hash tables have $O(1)$ worst-case behavior, at least amortized, when the data satisfies certain statistical conditions, and there ...