---
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`