Results 1  10
of
37
Efficient 2dimensional Approximate Matching of Halfrectangular Figures
, 1993
"... Efficient algorithms exist for the approximate two dimensional matching problem for rectangles. This is the problem of finding all occurrences of an m \Theta m pattern in an n \Theta n text with no more than k mismatch, insertion, and deletion errors. In computer vision it is important to general ..."
Abstract

Cited by 31 (11 self)
 Add to MetaCart
Efficient algorithms exist for the approximate two dimensional matching problem for rectangles. This is the problem of finding all occurrences of an m \Theta m pattern in an n \Theta n text with no more than k mismatch, insertion, and deletion errors. In computer vision it is important to generalize this problem to nonrectangular figures. We make progress towards this goal by defining halfrectangular figures of height m and area a. The approximate two dimensional matching problem for halfrectangular patterns can be solved using a dynamic programming approach in time O(an 2 ). We show an O(kn 2 p m log m p k log k + k 2 n 2 ) algorithm which combines convolutions with dynamic programming. Note that our algorithm is superior to previous known solutions for k m 1=3 . At the heart of the algorithm are the Smaller Matching Problem and the kAligned Ones with Location Problem. These are interesting problems in their own right. Efficient algorithms to solve both t...
Polytypic Pattern Matching
 In Conference Record of FPCA '95, SIGPLANSIGARCHWG2.8 Conference on Functional Programming Languages and Computer Architecture
, 1995
"... The (exact) pattern matching problem can be informally specified as follows: given a pattern and a text, find all occurrences of the pattern in the text. The pattern and the text may both be lists, or they may both be trees, or they may both be multidimensional arrays, etc. This paper describes a g ..."
Abstract

Cited by 28 (8 self)
 Add to MetaCart
The (exact) pattern matching problem can be informally specified as follows: given a pattern and a text, find all occurrences of the pattern in the text. The pattern and the text may both be lists, or they may both be trees, or they may both be multidimensional arrays, etc. This paper describes a general patternmatching algorithm for all datatypes definable as an initial object in a category of F algebras, where F is a regular functor. This class of datatypes includes mutual recursive datatypes and lots of different kinds of trees. The algorithm is a generalisation of the Knuth, Morris, Pratt like patternmatching algorithm on trees first described by Hoffmann and O'Donnell. 1 Introduction Most editors provide a search function that takes a string of symbols and returns the first position in the text being edited at which this string of symbols occurs. The string of symbols is called a pattern, and the algorithm that detects the position at which a pattern occurs is called a (exa...
An Alphabet Independent Approach to Two Dimensional Matching
, 1994
"... There are many solutions to the string matching problem which are strictly linear in the input size and independent of alphabet size. Furthermore, the model of computation for these algorithms is very weak: they allow only simple arithmetic and comparisons of equality between characters of the in ..."
Abstract

Cited by 24 (8 self)
 Add to MetaCart
There are many solutions to the string matching problem which are strictly linear in the input size and independent of alphabet size. Furthermore, the model of computation for these algorithms is very weak: they allow only simple arithmetic and comparisons of equality between characters of the input. In contrast, algorithm for two dimensional matching have needed stronger models of computation, most notably assuming a totally ordered alphabet. The fastest algorithms for two dimensional matching have therefore had a logarithmic dependence on the alphabet size. In the worst case, this gives an algorithm that runs in O(n log m) with O(m log m) preprocessing.
Approximate Pattern Matching with Samples
 In Proc. of ISAAC'94
, 1994
"... . We simplify in this paper the algorithm by Chang and Lawler for the approximate string matching problem, by adopting the concept of sampling. We have a more general analysis of expected time with the simplified algorithm for the onedimensional case under a nonuniform probability distribution ..."
Abstract

Cited by 22 (1 self)
 Add to MetaCart
. We simplify in this paper the algorithm by Chang and Lawler for the approximate string matching problem, by adopting the concept of sampling. We have a more general analysis of expected time with the simplified algorithm for the onedimensional case under a nonuniform probability distribution, and we show that our method can easily be generalized to the twodimensional approximate pattern matching problem with sublinear expected time. 1 Introduction Since the inaugural papers on string matching algorithms were published by Knuth, Morris and Pratt[11] and Boyer and Moore [5], the problem diversified into various directions. Let us call string matching onedimensional pattern matching. One is twodimensional pattern matching and the other is approximate pattern matching where up to k differences are allowed for a match. Yet another theme is twodimensional approximate pattern matching. There are numerous papers in these new research areas. We cite just a few of them to compare...
Optimally Fast Parallel Algorithms for Preprocessing and Pattern Matching in One and Two Dimensions
, 1993
"... All algorithms below are optimal alphabetindependent parallel CRCW PRAM algorithms. In one dimension: Given a pattern string of length m for the stringmatching problem, we design an algorithm that computes a deterministic sample of a sufficiently long substring in constant time. This problem use ..."
Abstract

Cited by 19 (10 self)
 Add to MetaCart
All algorithms below are optimal alphabetindependent parallel CRCW PRAM algorithms. In one dimension: Given a pattern string of length m for the stringmatching problem, we design an algorithm that computes a deterministic sample of a sufficiently long substring in constant time. This problem used to be a bottleneck in the pattern preprocessing for one and twodimensional pattern matching. The best previous time bound was O(log 2 m= log log m). We use this algorithm to obtain the following results. 1. Improving the preprocessing of the constanttime text search algorithm [12] from O(log 2 m= log log m) to O(log log m), which is now best possible. 2. A constanttime deterministic stringmatching algorithm in the case that the text length n satisfies n = \Omega\Gamma m 1+ffl ) for a constant ffl ? 0. 3. A simple probabilistic stringmatching algorithm that has constant time with high probability for random input. 4. A constant expected time LasVegas algorithm for computing t...
Fast Two Dimensional Pattern Matching
 Information Processing Letters
, 1993
"... An algorithm for searching for a two dimensional m \Theta m pattern in a two dimensional n \Theta n text is presented. It performs on the average less comparisons than the size of the text: n 2 =m using m 2 extra space. Basically, it uses multiple string matching on only n=m rows of the text. ..."
Abstract

Cited by 19 (4 self)
 Add to MetaCart
An algorithm for searching for a two dimensional m \Theta m pattern in a two dimensional n \Theta n text is presented. It performs on the average less comparisons than the size of the text: n 2 =m using m 2 extra space. Basically, it uses multiple string matching on only n=m rows of the text. It runs in at most 2n 2 time and is close to the optimal n 2 time for many patterns. It steadily extends to an alphabetindependent algorithm with a similar worst case. Experimental results are included for a practical version. 1 Introduction We address the problem of searching a two m \Theta m dimensional pattern in a two dimensional n \Theta n object (text). Our algorithm is based on any multiple stringsearching algorithm. First, it improves drastically on all other algorithms in the average case: O(n 2 =m) textpattern comparisons with O(m 2 ) extraspace versus (n 2 ; O(n)) or (Kn 2 ; O(m 2 )), (K ?? 1). It is the first algorithm we know of to be sublinear on average. Se...
Efficient 2dimensional approximate matching of nonrectangular figures
 Proc. of 2nd Symoposium on Descrete Algorithms
, 1991
"... Finding all occurrences of a nonrectangular pattern of height m and area a in an nn text with no more than k mismatch, insertion, and deletion errors is an important problem in computer vision. It can be solved using a dynamic programming approach in time O(an 2). We show a O(kn 2 # m log m # k log ..."
Abstract

Cited by 18 (7 self)
 Add to MetaCart
Finding all occurrences of a nonrectangular pattern of height m and area a in an nn text with no more than k mismatch, insertion, and deletion errors is an important problem in computer vision. It can be solved using a dynamic programming approach in time O(an 2). We show a O(kn 2 # m log m # k log k + k 2 n 2) algorithm which combines convolutions with dynamic programming. At the heart of the algorithm are the Smaller Matching Problem and the kAligned Ones with Location Problem. Efficient algorithms to solve both these problems are presented.
Approximate Subset Matching with Don't Cares
"... The Subset Matching problem was recently introduced by Cole and Hariharan. The input of the problem is a text array of n sets totaling s elements and a pattern array of m sets totaling s0 elements. There is a match of the pattern in a text location if every pattern set is a subset of the correspondi ..."
Abstract

Cited by 13 (1 self)
 Add to MetaCart
The Subset Matching problem was recently introduced by Cole and Hariharan. The input of the problem is a text array of n sets totaling s elements and a pattern array of m sets totaling s0 elements. There is a match of the pattern in a text location if every pattern set is a subset of the corresponding text set. Subset matching has proven to be a powerful technique and enabled finding an efficient solution to the Tree Matching problem. The subset matching model may prove useful in solving other hard problems, e.g. Swap Matching. In this paper we investigate the complexity of approximate subset matching with "don't care"s. We provide two algorithms for the problem. A randomized algorithm whose complexity is O((s + n + n m s 0)pm log2 m) and a deterministic algorithm whose complexity is O((s + n)ps0 log m).
Two Dimensional Dictionary Matching
 Information Processing Letters
, 1992
"... Most traditional pattern matching algorithms solve the problem of finding all occurrences of a given pattern string P in a given text T . Another important paradigm is the dictionary matching problem. Let D = {P 1 , ..., P k } be the dictionary. We seek all locations of dictionary patterns that a ..."
Abstract

Cited by 12 (3 self)
 Add to MetaCart
Most traditional pattern matching algorithms solve the problem of finding all occurrences of a given pattern string P in a given text T . Another important paradigm is the dictionary matching problem. Let D = {P 1 , ..., P k } be the dictionary. We seek all locations of dictionary patterns that appear in a given text T .