CN114840726A - Method for realizing character string storage and search by hash table - Google Patents
Method for realizing character string storage and search by hash table Download PDFInfo
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- G06F16/90344—Query processing by using string matching techniques
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- G06F16/901—Indexing; Data structures therefor; Storage structures
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Abstract
The invention discloses a method for realizing character string storage and search by a hash table, which relates to the technical field of hash tables and comprises S1 and collision orders of character strings; s2, counting collision orders; s3, storing the character strings into a hash table and S4 according to the collision order, and searching the position of the character strings in the hash table. Compared with a general method in a standard library, the method for realizing the storage and the search of the character string by the hash table greatly improves the character string query efficiency, greatly reduces the delay and the jitter in the transaction process, ensures that a transaction system realized by software achieves the performance of a transaction system realized by hardware, and is favorable for improving the character string search performance in a high-frequency transaction counter realized by software.
Description
Technical Field
The invention relates to the technical field of hash tables, in particular to a method for realizing character string storage and search by a hash table.
Background
The character string search is the content that must be related to in all software engineering and projects, the hash table is a classic data structure, it is one of the core methods to deal with character string storage and search too, in most scenes that the performance requirement is not high, usually use the tool that the standard library provides to realize the storage and search of the character string, it is a common method, can meet most demands.
The high-frequency trading counter in the market at present has two realization modes: one is realized by hardware, the other is realized by software, the hardware has the advantages of fast data processing and low jitter, but has the defect of high development cost, the software has the advantages of slow data processing and high jitter, but the development cost is low, the problem of the speed of data processing is solved when a software high-frequency trading counter is realized, and one of the cores is to improve the character string searching performance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for realizing character string storage and search by a hash table, which solves the problems in the background technology.
In order to achieve the purpose, the invention is realized by the following technical scheme: a method for realizing character string storage and search by a hash table comprises the following operation steps:
s1, collision order of character strings:
determining the length of a hash table according to the number of the character strings, marking the length as Len, calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
the longest character string is 16 bytes;
s2, collision order statistics:
because different character strings str have the probability of obtaining the same position value pos, namely different character strings have conflicts, the conflicts need to be solved;
recording the pos value obtained for the first time, wherein the collision sequence is 1; obtaining pos value for the second time, wherein the collision order is 2; by analogy, recording the collision order map [ str ] ═ seq [ pos ] of the character string str at the position pos;
s3, storing the character strings into a hash table according to the collision order:
traversing all the character strings according to the collision sequence, wherein the collision sequence is from low to high, namely max (seq [ pos ]) is traversed, and all the character strings are traversed each time;
s4, finding the position of the character string in the hash table:
calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
and jumping to a corresponding position of the hash table, and checking whether the character string of the current position is equal to the target character string.
Further, in the step S2, seq [ pos ] indicates a pos collision order.
Further, in the step S3, the detailed steps are as follows:
(1) setting the collision sequence as N, and traversing all character strings from 1;
(1-1) if the collision order of the character strings is not the same as N, the step is circulated.
Further, (1-2) if the collision order of the character strings is the same as N and the position corresponding to the pos value is null, storing the character strings in the position, and turning to the step (1-1).
Further, (1-3) if the current location pointer is not null, then jump to the next location pointed to by the pointer and check the next location pointer, looping this step.
Further, (1-4) if the pointer of the current position is null, finding a free position backwards in the hash table, storing the character string in the position, and letting the pointer of the last position point to the position, and turning to step (1-1).
Further, (1-5) if the collision order is N traversal ends, N is equal to N +1, if N is less than or equal to max (seq [ pos ]), go to step (1), otherwise, end.
Further, in the step S4, if the character string of the current location is equal to the target character string, the process is ended, otherwise, it is checked whether the pointer is empty.
And further, if the checking pointer is null, ending, otherwise, turning to the step (1-1) according to the pointer value.
Furthermore, the method for realizing character string storage and search by the hash table is applied to the field of data processing.
The invention provides a method for realizing character string storage and search by a hash table, which has the following beneficial effects:
compared with a general method in a standard library, the method for realizing the storage and the search of the character string by the hash table greatly improves the character string query efficiency, greatly reduces the delay and the jitter in the transaction process, ensures that a transaction system realized by software achieves the performance of a transaction system realized by hardware, and is favorable for improving the character string search performance in a high-frequency transaction counter realized by software.
Drawings
FIG. 1 is a schematic flow chart illustrating the collision order of statistical strings in a method for implementing string storage and search by a hash table according to the present invention;
FIG. 2 is a schematic flow chart illustrating a method for storing and searching a character string in a hash table according to a collision order according to the present invention;
FIG. 3 is a schematic diagram of a first traversal of a method for implementing string storage and search by a hash table according to the present invention;
FIG. 4 is a schematic diagram illustrating a second traversal of a method for implementing string storage and search by using a hash table according to the present invention;
fig. 5 is a schematic flow chart illustrating a process of searching for a position of a character string in a hash table according to a method for implementing character string storage and search by using the hash table of the present invention.
Detailed Description
Referring to fig. 1 to 5, the present invention provides a technical solution: a method for realizing character string storage and search by a hash table comprises the following operation steps:
s1, collision order of character strings:
determining the length of a hash table according to the number of the character strings, marking the length as Len, calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
the longest character string is 16 bytes;
s2, collision order statistics:
because different character strings str have the probability of obtaining the same position value pos, namely different character strings have conflicts, the conflicts need to be solved;
recording pos values obtained for the first time, wherein the collision sequence is 1; obtaining pos value for the second time, wherein the collision order is 2; by analogy, recording the collision order map [ str ] ═ seq [ pos ] of the character string str at the position pos;
s3, storing the character strings into a hash table according to the collision order:
traversing all the character strings according to the collision sequence, wherein the collision sequence is from low to high, namely max (seq [ pos ]) is traversed, and all the character strings are traversed each time;
s4, finding the position of the character string in the hash table:
calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
and jumping to a corresponding position of the hash table, and checking whether the character string at the current position is equal to the target character string.
In the step S2, seq [ pos ] indicates a pos collision order.
In step S3, the detailed steps are as follows:
(1) setting the collision sequence as N, and traversing all character strings from 1;
(1-1) if the collision order of the character strings is not the same as N, the step is circulated.
(1-2) if the collision order of the character strings is the same as N and the position corresponding to the pos value is empty, storing the character strings at the position, and turning to the step (1-1).
(1-3) if the current position pointer is not null, jumping to the next position pointed by the pointer and checking the next position pointer, and circulating the step.
(1-4) if the pointer of the current position is null, finding a free position backwards in the hash table, storing the character string in the position, and enabling the pointer of the last position to point to the position, and turning to the step (1-1).
(1-5) if the collision order is that N traversal ends, then N is equal to N +1, if N is less than or equal to max (seq [ pos ]), then go to step (1), otherwise end.
In step S4, if the character string of the current position is equal to the target character string, the process is ended, otherwise, it is checked whether the pointer is empty.
If the checking pointer is null, ending, otherwise, turning to the step (1-1) according to the pointer value.
The method for realizing character string storage and search by the hash table is applied to the field of data processing.
In summary, the hash table implements a method for storing and searching a character string, and the embodiment of the method includes:
assume that there is a string hash value set containing 10 elements, and a hash table with a storage length of 11;
hash value set: {48,35,64,29,76,40,15,50,44,65 };
then they are stored in the following hash table:
a first traversal processing the hash value of the character string with the collision order of 1 (as shown in fig. 3), and a second traversal processing the hash value of the character string with the collision order of 2 (as shown in fig. 4);
description of the drawings: the hash table has a length of 11, the first position index is 0, the last position index is 10, and a pointer of 5 indicates a position pointing to an index of 5.
The invention provides a method for realizing character string storage and search by a hash table, which has the following beneficial effects:
compared with a general method in a standard library, the method for realizing the storage and the search of the character string by the hash table greatly improves the character string query efficiency, greatly reduces the delay and the jitter in the transaction process, ensures that a transaction system realized by software achieves the performance of a transaction system realized by hardware, and is favorable for improving the character string search performance in a high-frequency transaction counter realized by software.
Referring to fig. 1 to fig. 5, in summary, the method for implementing string storage and lookup by using the hash table includes the following steps:
s1, collision order of character strings:
determining the length of a hash table according to the number of the character strings, marking the length as Len, calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
the longest character string is 16 bytes;
s2, collision order statistics:
because different character strings str have the probability of obtaining the same position value pos, namely different character strings have conflicts, the conflicts need to be solved;
recording the pos value obtained for the first time, wherein the collision sequence is 1; obtaining pos value for the second time, wherein the collision order is 2; by analogy, recording the collision order map [ str ] ═ seq [ pos ] of the character string str at the position pos;
wherein seq [ pos ] represents a pos collision order;
s3, storing the character strings into a hash table according to the collision order:
traversing all the character strings according to the collision sequence, wherein the collision sequence is from low to high, namely max (seq [ pos ]) is traversed, and all the character strings are traversed each time;
the detailed steps are as follows:
(1) setting the collision sequence as N, and traversing all character strings from 1;
(1-1) if the collision order of the character strings is not the same as N, the step is circulated.
(1-2) if the collision order of the character strings is the same as N and the position corresponding to the pos value is empty, storing the character strings at the position, and turning to the step (1-1).
(1-3) if the current position pointer is not null, jumping to the next position pointed by the pointer and checking the next position pointer, and circulating the step.
(1-4) if the pointer of the current position is null, finding a free position backwards in the hash table, storing the character string in the position, and enabling the pointer of the last position to point to the position, and turning to the step (1-1).
(1-5) if the collision order is that N traversal ends, then N is equal to N +1, if N is less than or equal to max (seq [ pos ]), then go to step (1), otherwise, end;
s4, finding the position of the character string in the hash table:
calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
jumping to a corresponding position of a hash table, and checking whether the character string at the current position is equal to the target character string;
if the character string of the current position is equal to the target character string, ending, otherwise, checking whether the pointer is empty;
if the checking pointer is null, ending, otherwise, turning to the step (1-1) according to the pointer value.
The invention provides a method for realizing character string storage and search by a hash table, which has the following beneficial effects:
compared with a general method in a standard library, the method for realizing the storage and the search of the character string by the hash table greatly improves the character string query efficiency, greatly reduces the delay and the jitter in the transaction process, ensures that a transaction system realized by software achieves the performance of a transaction system realized by hardware, and is favorable for improving the character string search performance in a high-frequency transaction counter realized by software.
Claims (10)
1. A method for realizing character string storage and search by a hash table is characterized in that: the method for realizing the storage and the search of the character string by the hash table comprises the following operation steps:
s1, collision order of character strings:
determining the length of a hash table according to the number of the character strings, marking the length as Len, calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
the longest character string is 16 bytes;
s2, counting collision order:
because different character strings str have the probability of obtaining the same position value pos, namely different character strings have conflicts, the conflicts need to be solved;
recording the pos value obtained for the first time, wherein the collision sequence is 1; obtaining pos value for the second time, wherein the collision order is 2; by analogy, recording the collision order map [ str ] ═ seq [ pos ] of the character string str at the position pos;
s3, storing the character strings into a hash table according to the collision order:
traversing all the character strings according to the collision sequence, wherein the collision sequence is from low to high, namely max (seq [ pos ]) is traversed, and all the character strings are traversed each time;
s4, finding the position of the character string in the hash table:
calculating a hash value A of the character string str, and then performing modular operation on the A to obtain a position pos in the hash table;
wherein hash (str) ═ a; a mode Len ═ pos;
and jumping to a corresponding position of the hash table, and checking whether the character string of the current position is equal to the target character string.
2. The method of claim 1, wherein the hash table stores and searches a string, and further comprising: in the step S2, seq [ pos ] indicates a pos collision order.
3. The method of claim 1, wherein the hash table stores and searches strings, and comprises: in the step S3, the detailed steps are as follows:
(1) setting the collision sequence as N, and traversing all character strings from 1;
(1-1) if the collision order of the character strings is not the same as N, the step is circulated.
4. The method of claim 3, wherein the hash table stores and searches a string, and further comprising: (1-2) if the collision order of the character strings is the same as N and the position corresponding to the pos value is empty, storing the character strings at the position, and turning to the step (1-1).
5. The method of claim 3, wherein the hash table stores and searches a string, and further comprising: (1-3) if the current position pointer is not null, jumping to the next position pointed by the pointer and checking the next position pointer, and circulating the step.
6. The method of claim 3, wherein the hash table stores and searches a string, and further comprising: (1-4) if the pointer of the current position is null, finding a free position backwards in the hash table, storing the character string in the position, and enabling the pointer of the last position to point to the position, and turning to the step (1-1).
7. The method of claim 3, wherein said hash table is used for storing and searching character strings, and is characterized in that: (1-5) if the collision order is that N traversal ends, then N is equal to N +1, if N is less than or equal to max (seq [ pos ]), then go to step (1), otherwise end.
8. The method of claim 1, wherein the hash table stores and searches a string, and further comprising: in the step S4, if the character string of the current position is equal to the target character string, the process is ended, otherwise, it is checked whether the pointer is empty.
9. The method of claim 8, wherein the hash table stores and searches a string, and further comprising: if the checking pointer is null, ending, otherwise, turning to the step (1-1) according to the pointer value.
10. The method for storing and searching character strings by using the hash table according to any of claims 1-9, wherein: the method for realizing character string storage and search by the hash table is applied to the field of data processing.
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| CN202210537791.6A CN114840726A (en) | 2022-05-17 | 2022-05-17 | Method for realizing character string storage and search by hash table |
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