Difference between revisions of "Intermediate C++ Game Programming Tutorial 24"
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*:- <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> | ||
| − | + | * multimap does not have an index operator <code>[]</code> [https://youtu.be/JlPsCoCO99o?t=25m21s 25:21] | |
</div> | </div> | ||
[https://youtu.be/LsjFAx-dG5I Tutorial 24.2] | [https://youtu.be/LsjFAx-dG5I Tutorial 24.2] | ||
Revision as of 04:30, 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
[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- 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
- The
std::multimapandstd::multisetclasses 21:28- Map has unique keys, with multimap you can insert multiple elements with the same key
- This enables operations like
std::multimap::equal_rangethat returns a pair of iterators (begin and end) of the range where these elements have that same key -
std::multimap::countwill return the number of elements with specific key
- Practical example of multimap use case 22:30
- Implementation example of a custom Comparison functor for the
Vei2class (2D coordinate vector).
- - Chili's choice for ordering (used in the body of the functor):
- -
return (lhs.x == rhs.x) ? lhs.y < rhs.y : lhs.x < rhs.x;
- Example of how to find and print multiple elements in a multimap using
equal_range()
- Implementation example of a custom Comparison functor for the
- multimap does not have an index operator
[]25:21
- [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.
