Associative arrays/Creation/C: Difference between revisions
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(→From Scratch: include headers, use hash_t instead of Hash as struct name) |
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A hash table can be implemented with the following. Because of this example's simplicity, it comes with some restrictions on use and capabilities: It can't be resized automatically, if you try to insert more values than its capacity it will freeze, the hashing function is very simple, etc. All are fixable with additional logic or using a library: |
A hash table can be implemented with the following. Because of this example's simplicity, it comes with some restrictions on use and capabilities: It can't be resized automatically, if you try to insert more values than its capacity it will freeze, the hashing function is very simple, etc. All are fixable with additional logic or using a library: |
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< |
<syntaxhighlight lang="с">#include <stdio.h> |
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#include <stdlib.h> |
#include <stdlib.h> |
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printf("a => %s\n", hash_lookup(h, "a")); |
printf("a => %s\n", hash_lookup(h, "a")); |
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return 0; |
return 0; |
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}</<syntaxhighlight> |
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}</lang> |
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==Libraries== |
==Libraries== |
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{{libheader|Judy}} |
{{libheader|Judy}} |
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< |
<syntaxhighlight lang="с">#include <stdio.h> |
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#include <Judy.h> |
#include <Judy.h> |
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return 0; |
return 0; |
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}</ |
}</syntaxhighlight> |
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{{libheader|Judy}} |
{{libheader|Judy}} |
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We can easily iterate over pair of keys (indexes) and values. |
We can easily iterate over pair of keys (indexes) and values. |
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< |
<syntaxhighlight lang="с">#include <stdio.h> |
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#include <Judy.h> |
#include <Judy.h> |
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JudySLFreeArray(&assoc_arr, PJE0); |
JudySLFreeArray(&assoc_arr, PJE0); |
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return 0; |
return 0; |
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}</ |
}</syntaxhighlight> |
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===POSIX hsearch()=== |
===POSIX hsearch()=== |
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{{libheader|POSIX}} |
{{libheader|POSIX}} |
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< |
<syntaxhighlight lang="с">#include <inttypes.h> /* intptr_t, PRIxPTR */ |
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#include <search.h> /* hcreate(), hsearch() */ |
#include <search.h> /* hcreate(), hsearch() */ |
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#include <stdio.h> /* perror(), printf() */ |
#include <stdio.h> /* perror(), printf() */ |
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*/ |
*/ |
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return 0; |
return 0; |
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}</ |
}</syntaxhighlight> |
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<pre>red has value ff0000 |
<pre>red has value ff0000 |
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====To delete or iterate==== |
====To delete or iterate==== |
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{{libheader|POSIX}} |
{{libheader|POSIX}} |
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< |
<syntaxhighlight lang="с">#include <inttypes.h> |
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#include <search.h> |
#include <search.h> |
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#include <stdio.h> |
#include <stdio.h> |
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return 0; |
return 0; |
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}</ |
}</syntaxhighlight> |
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<pre>5 is not deleted |
<pre>5 is not deleted |
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{{works with|OpenBSD|4.8}} |
{{works with|OpenBSD|4.8}} |
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< |
<syntaxhighlight lang="с">#include <sys/types.h> |
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#include <err.h> /* err() */ |
#include <err.h> /* err() */ |
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number_example(); |
number_example(); |
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return 0; |
return 0; |
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}</ |
}</syntaxhighlight> |
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Output: |
Output: |
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{{works with|OpenBSD|4.8}} |
{{works with|OpenBSD|4.8}} |
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< |
<syntaxhighlight lang="с">#include <sys/tree.h> |
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#include <err.h> /* err() */ |
#include <err.h> /* err() */ |
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number_example(); |
number_example(); |
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return 0; |
return 0; |
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}</ |
}</syntaxhighlight> |
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Output: |
Output: |
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