# Questions tagged [search-algorithms]

Algorithms for finding an element in some specified data-structure (most commonly, in a tree).

160 questions with no upvoted or accepted answers
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### Stopping condition for goal-directed bidirectional search for shortest path

So I have a graph and need to find shortest path between two points in it. I need1 to do it it using bidirectional search. The bidirectional search should be goal-directed, i.e. A*. So let $l(u,v)$ ...
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### Find maximum in array without comparisons between elements

Suppose $A$ is an array of integers, $|A|=n$, $A=\{a_i|1\leq a_i\leq N, i=1\ldots n\}$. The goal is to find an efficient algorithm $\cal{F}$ to find maximum element in $A$ with these restrictions: ...
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### Understanding the Baeza-Yates Régnier algorithm (multiple string matching, extended from Boyer-Moore)

First of all, excuse me if I write a lot, I tried to summarize my research so that everyone can understand. R. Baeza-Yates and M. Regnier published in 1993 a new algorithm for searching a two ...
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### Merge sort in place

I don't quite understand why in-place sort merge sort isn't preferred over not-in place? Is it because theoretically in place merge sort is better because of its memory complexity tradeoff, but in ...
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### Searching a bitonic array with roughly $2\log n$ comparisons

I don't know how to search a bitonic array with roughly $2\log n$ comparisons in the worst case. What I am trying now is to find the maximum integer using roughly $\log n$ comparisons (binary search) —...
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### How do search engines implement fuzzy search?

Googling "large horse walks into house" also returns results that contain "large horse in a house" and "the house has large horses". How is Google able to return near-...
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### Using graph symmetries to speed up subgraph enumeration

I have an undirected graph $G$. It has some symmetries in the sense that I know it's automorphism group $\text{Aut}(G)$. I am searching for a specific subgraph defined by some constraints $\phi$ and ...
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### Any elegant approach to search where users have permissions on subset of records?

I work in Search and have seen following problem appear in different forms. There are many users in an enterprise; they have ability to create records. Each user has variable level of access to some ...
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### Why are the conditions for optimality different for A* tree and graph search?

I am unclear as to why the conditions for optimality for A* search are different for graph search and tree search. When discussing conditions for optimality for A* search in Russell and Norvig's ...
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### KMP Algorithm, Pratt's Minimisation/optimization of Knuth's original DFA based algorithm

The Original Knuth's Algorithm is based on DFA and it depends on the alphabet size. And Then, Pratt optimised it to be independent of Alphabet Size. But, All the ...
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### Fastest algorithm for shortest path with atmost k edges on a DAG with non-negative edge weights?

(Please note, this is not a duplicate to Shortest path with exactly $k$ edges OR Shortest path with a fixed number of edges. What I want is a better algorithm) The problem under consideration is to ...
187 views

### Remove a subsequence from a string and append it at the end

Consider the following operation on strings: pick a (not necessarily contiguous) subsequence, remove it and then append all the characters in the same order at the end. This operation preserves the ...
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### Intellij string search and highlight algorithm

I'm searching for an alogrithm that takes two strings, a query and a string that is to be searched for the query. The algorithm should result in a 'found' when the string contains the characters of ...
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### Should a prefix tree (trie) node store only a single character or a string?

I've just implemented a Trie and I thought it would be a good idea to store strings in the Trie nodes in contrast to storing single characters. Storing strings is for sure more space-efficient and ...
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### Efficient approximation for find all the nodes and edges which match with some sub-tree in a graph

Let's suppose that I have a big digraph D and a small tree T (small w.r.t D), both directed, D can be connected or not, but T is connected. Here an example: Let's say that D is as follow: And T is ...
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### Post's Correspondence Problem - BFS or DFS?

This question has recently occurred to me as I was working on an implementation of the (Bounded) Post's Correspondence Problem. Basically, which method is generally best for PCP? Breadth-first or ...
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### A case study for search techniques in AI

We are teaching an artificial intelligence class and we need a different case study other than geographical maps (the popular example is the map of Romania) to explain the difference between Breadth-...
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### Estimating size of state space

I have been studying search problems in AI, and I am having some troubles understanding some points in these concepts: State Space: "represents the environment of the problem, the set of all states ...
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### How to make an anytime version of alpha beta pruning?

I wish to use alpha beta pruning in a problem with following constraints: Terminal nodes are likely too distant to be found in most searches Instead I want to maximize an evaluation function There ...
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### How to efficiently create balanced KD-Trees from a static set of points

From Wikipedia, KD-Trees: Alternative algorithms for building a balanced k-d tree presort the data prior to building the tree. They then maintain the order of the presort during tree construction ...
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### Why is exact nearest neighbor search hard in high dimensional spaces?

I started research on nearest neighbor search in IR a couple of weeks ago. I am still very new to this field, but what I discovered so far from literature is: 1) For the exact nearest neighbor ...
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### What limits the implementation of proximity operators for text indexing and searching?

I was asking on academia.se, if anyone knows scientific search engines offering a proximity operator like Google Web Search does, while Google Scholar Search does not. That's sad, because this ...
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### Estimating size of state space search problem

Im currently enrolled in an AI course and we are starting with state space search problems. My professor always seems to ask, given a certain problem, what is the estimate size of the state space? It'...
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1 vote