Difference between revisions of "Intermediate C++ Game Programming Tutorial 24"
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* The <code>std::set<KeyType></code> class [https://youtu.be/JlPsCoCO99o?t=20m00s 20:00] | * The <code>std::set<KeyType></code> class [https://youtu.be/JlPsCoCO99o?t=20m00s 20:00] | ||
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** With a set, you only have keys, and a unique entry for each unique key | ** With a set, you only have keys, and a unique entry for each unique key | ||
** Use case: ensure that there are no duplicates in a set | ** Use case: ensure that there are no duplicates in a set | ||
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* The <code>std::multimap</code> and <code>std::multiset</code> classes [https://youtu.be/JlPsCoCO99o?t=21m28s 21:28] | * The <code>std::multimap</code> and <code>std::multiset</code> classes [https://youtu.be/JlPsCoCO99o?t=21m28s 21:28] | ||
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** Map has unique keys, with multimap you can insert multiple elements with the same key | ** Map has unique keys, with multimap you can insert multiple elements with the same key | ||
** This enables operations like <code>std::multimap::equal_range</code> that returns a pair of iterators (begin and end) of the range where these elements have that same key | ** This enables operations like <code>std::multimap::equal_range</code> that returns a pair of iterators (begin and end) of the range where these elements have that same key | ||
** <code>std::multimap::count</code> will return the number of elements with specific key | ** <code>std::multimap::count</code> will return the number of elements with specific key | ||
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* Practical example of multimap use case [https://youtu.be/JlPsCoCO99o?t=22m30s 22:30] | * Practical example of multimap use case [https://youtu.be/JlPsCoCO99o?t=22m30s 22:30] | ||
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** Implementation example of a custom Comparison functor for the <code>Vei2</code> class (2D coordinate vector). | ** Implementation example of a custom Comparison functor for the <code>Vei2</code> class (2D coordinate vector). | ||
*:- Chili's choice for ordering (used in the body of the functor): | *:- Chili's choice for ordering (used in the body of the functor): | ||
*:- <code>return (lhs.x == rhs.x) ? lhs.y < rhs.y : lhs.x < rhs.x;</code> | *:- <code>return (lhs.x == rhs.x) ? lhs.y < rhs.y : lhs.x < rhs.x;</code> | ||
** Example of how to find and print multiple elements in a multimap using <code>equal_range()</code> | ** Example of how to find and print multiple elements in a multimap using <code>equal_range()</code> | ||
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* multimap does not have an index operator <code>[]</code> [https://youtu.be/JlPsCoCO99o?t=25m21s 25:21] | * multimap does not have an index operator <code>[]</code> [https://youtu.be/JlPsCoCO99o?t=25m21s 25:21] | ||
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** When you do a lookup on a multimap, you should use <code>equal_range()</code> | ** When you do a lookup on a multimap, you should use <code>equal_range()</code> | ||
** The problem with <code>find()</code> on a multimap, is that if there are several elements with key in the ccontainer, any of them may be returned | ** The problem with <code>find()</code> on a multimap, is that if there are several elements with key in the ccontainer, any of them may be returned | ||
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[https://youtu.be/LsjFAx-dG5I Tutorial 24.2]: The unordered associative containers | [https://youtu.be/LsjFAx-dG5I Tutorial 24.2]: The unordered associative containers | ||
Revision as of 04:38, 20 January 2020
Associative containers are super useful, both as a convenient fast way to create dictionary or mapping for real-world problems like managing game resources, and as a data structure to help solve more abstract algorithmic computer science problems. And hash tables are fast as balls.
Contents
[hide]Topics Covered
Part 1
-
std::mapcontainer interface - Binary tree data structure
-
std::mapkey requirements (comparison) -
std::mapgotchas (std::remove_ifandconstkeys) -
std::set -
std::multimapandstd::multiset
Part 2
- Hash table performance vs. binary tree performance
- Hash table data structure
-
std::unordered_mapkey requirements - Hash combining
-
std::unordered_mapbucket interface and hashing policy - When to choose
std::mapoverstd::unordered_map
Video Timestamp Index
Tutorial 24.1: The ordered associative containers
[Expand]
- The
std::map<KeyType,ValueType>class 0:46
- The Binary tree data structure 2:46
- A look at the
std::mapcppreference.com documentation: Insert, Lookup, Find 7:35
- Requirements on KeyType 14:30
-
std::mapcppreference.com documentation continued: Erase 15:28
- Two <<important>> things to know when working with associative containers 16:04
- The
std::set<KeyType>class 20:00
- The
std::multimapandstd::multisetclasses 21:28
- Practical example of multimap use case 22:30
- multimap does not have an index operator
[]25:21
Tutorial 24.2: The unordered associative containers
- [WORK-IN-PROGRESS]
Homework Assignment
The homework for this video is to enable use of a custom datatype in unordered_map hashing over multiple (4) members of that datatype. The solution video is here.
