Questions tagged [search]
52 questions
14
votes
3 answers
Why are search problems assumed to have the structure of "find a path in a graph"?
I have skimmed a few introductions to "search problems", and I have noticed that:
Stated informally search problems are defined as "find an object y inside a larger space/object X"
But when defining exact algorithms, search problems are thought of…
user56834
- 4,244
- 5
- 21
- 35
10
votes
1 answer
Why Is KD-Tree-based Nearest Neighbor Exponential in K?
I've read in many papers on higher-dimensional nearest neighbor search that KD-Trees are exponential in K, but I can't seem to determine why.
What I'm looking for is a solid runtime-complexity analysis which explains this aspect of the problem.
akdom
- 200
- 5
7
votes
1 answer
What is the most recent comparison of signature files and inverted indices?
Modern papers on search indices often contain a statement that inverted indexes (posting lists) are categorically superior to signature files (bloom filters). Here are some examples from papers published in 2016:
While this [signature file]…
dan
- 529
- 2
- 7
6
votes
1 answer
Is there a polynomial time algorithm to determine whether an 'up down' language is 'emptible'?
Definitions:
An up down language is a language whose alphabet is a set of pairs, but not characters, of two characters, where the one character in the pair is the opposite of the other character in the pair.
Each word in the language is…
Farewell Stack Exchange
- 371
- 2
- 17
6
votes
2 answers
Understanding Levin's Universal Search
I am having troubles understanding Levin's universal search method. In Scholarpedia, http://www.scholarpedia.org/article/Universal_search, it is claimed that “If there exists a program $p$, of length $l(p)$, that can solve the problem in time $t$,…
Don Arturo
- 91
- 1
- 4
4
votes
1 answer
How come Google search never gets slower? Doesn't it have to go through the ever increasing amount of data on the internet and then rank?
I heard Google creates indexes of pages. Even then, the number of indexes goes with time. Why wouldn't this slow down the search?
user14706
- 43
- 3
4
votes
1 answer
Heuristics vs meta-heuristics vs hyper-heuristics?
The wikipedia page on meta-heuristics states that they are "heuristics designed to find, generate, or select a heuristic".
The wikipedia page on hyper-heuristics states that they are "heuristic search methods that seeks to automate [...] the process…
user626625
- 165
- 7
3
votes
2 answers
Why does an admissible heuristic mean A* is optimal?
An admissible heuristic never overestimates the cost to reach the goal. However, isn't that only the relative difference between heuristics for two different paths matter?
Say we have optimal path A (cost 100 to reach goal) and sub-optimal path Z…
Laura K
- 33
- 3
3
votes
3 answers
Does White never lose in Chess if Chess is solved?
If the machine has enough memory and speed as to compute all states of the Chess game in a reasonable time, can a player with the white pieces - operated by a machine - lose a game?
108880
- 27
- 1
- 11
3
votes
1 answer
Finding $k$-th element in prefix of size $i$
Let's say we are given array $A$ of size $n$. We need to answer some numbers of queries. For each query we are given index $i$ and integer value $k$, $k \le i$. If we take the first $i$ elements of the array $A$ and we sort them we should return the…
someone12321
- 1,428
- 15
- 27
2
votes
0 answers
B/B+ trees without leftmost pointers
In both B-trees and B+trees, a node (a.k.a page) contains K keys and K+1 pointers:
node = [ ptr_1, key_1, ... , ptr_K , key_K , ptr_(K+1) ]
Now suppose that I want a B/B+ tree (whichever possible), where each node contains exactly K keys and K…
Ali
- 121
- 5
2
votes
1 answer
How does topic or tag suggestion algorithms work?
I know it's a keyword based search. But sites like Quora have some good suggesting algorithms where the algorithm understands the intent of question asked rather than just the keywords meanings.
For instance, for a question involving "O(n^2)" it…
Himanshu Kansal
- 121
- 2
2
votes
2 answers
Non-quadratic search for specific difference between elements in sorted array
New to computer science and am attempting to verify if there are any non-quadratic approaches (i.e. better performance than Big-O of n^2) for finding a potential specific difference between either adjacent or nonadjacent elements in a sorted array…
AdjunctProfessorFalcon
- 121
- 4
2
votes
1 answer
special case of best first search algorithms
I read somewhere that DFS is a special case of Best first search algorithm if f(n)=-depth(n). please justify this i am not getting it.:/
mehru
- 21
- 2
2
votes
3 answers
Fast comparison with a tolerance
I am trying to find a way to compare two real numbers (actually floating-point) with a tolerance, i.e. test $|r-s|\le\epsilon$. Without loss of generality, $\epsilon=1$.
I want to do this by replacing the numbers by a discrete key computed on them…
user16034