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+---
+title: C++ Data Structures
+created_date: 2024-11-11
+updated_date: 2024-11-11
+aliases:
+tags:
+---
+# C++ Data Structures
+
+## Vectors
+- stores sequence of data in variable length container (like an array, but variable in size)
+- insertions other than at the end are slow, because elements must be shifted
+- Applications:
+	- Paths and Waypoints and trajectories
+	- Vectors of vectors allow to store matrices
+	- dynamic resizing
+	- any element can be accessed --> random access
+	- access all element at once, filter, sort them, etc
+## Stack and Queues
+- storing data in specific order
+### Stack
+- LIFO: Last in first out
+	- meaning if i stack 1 then 2 then 3 and then I pop them I get 3 first, then 2 and finally 1
+	- 1,2,3 --> 3,2,1
+- Applications
+	- Backtracking algorithms: if you hit a dead end and you need to go back to a previous node from where you can explore another path.
+	- Depth first search
+	- Undo/Redo functionality (last action must be undone first)
+	- store navigation history (web browsers)
+	- manage states (you could go back to a previous state)
+### Queues
+- FIFO: First in First Out
+	- 1,2,3 --> 1,2,3
+- Applications:
+	- Buffers of sensors
+	- moving average implementation
+	- data streaming
+
+## Sets
+- collection of **unique** elements
+- you cannot modify elements of a set
+- ordered and unordered sets
+- Applications
+	- UID management:
+		- keep track of objects in a scene (label each with a unique id) --> robotics navigation, etc.
+	- Store valid configuration sets for system. Invalid configurations can be detected
+	- Keep track of visited nodes/cells in grid. unordered cell --> very fast lookup if cell has already been visited
+	- Union, intersections and difference
+		- used in multi robot systems.
+	- Feature and Capabillity Tracking: Keep track of which sensors are online, which features are working
+	- Finite State Machines and Transitions: keep track of allowed states and prevent illegal ones
+## Arrays
+- fixed size
+- useful for limited memory tasks
+
+## Hash Map
+- collection of unique elements as key-value pairs. Access them through `.first` and `.secondo`