formal-notes/Formal Lang.md
2025-01-22 15:05:47 -06:00

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# Chapter 0
dont do np hard problems
# Define
## Computability Theory
1930s - 1950s
What can be computed?
## Automata Theory
1930s - 1950s
How does making changes o the underlying model effect computational power?
## Complexity Theory
1960s - Present
What is computable in practice?
P vs. NP
# Graph Theory?
## Define
### Subgraph
Let $G = \{V_G, E_G\}$ and $H = \{V_H, E_H\}$
$G$ is a subgraph of $H$ if
1. $V_A = V_H$
2. $E_G \subset E_H + \forall(v_1, v_2)$
### Path
Hits vertices in a graph
Simple Graph: only hits vertices once
Cycle: There's some sort of loop in the graph
Simple Cycle: Only repeated node is the first and last one
Tree
Directed Graph: a graph that is made up of a set of vertices connected by directed edges
Strongly Connected: A directed graph is strongly connected if a directed path connects every two nodes.
# Strings & Languages
Alphabet: Non-empty finite set
Symbol: Member of alphabet
String: Sequence of symbols
Language: Set of strings