diff --git a/notes/.obsidian/plugins/obsidian-to-anki-plugin/data.json b/notes/.obsidian/plugins/obsidian-to-anki-plugin/data.json index 0885640..ecbd182 100644 --- a/notes/.obsidian/plugins/obsidian-to-anki-plugin/data.json +++ b/notes/.obsidian/plugins/obsidian-to-anki-plugin/data.json @@ -197,7 +197,12 @@ "lcrs-nodes.png", "binary-tree-nodes.png", "archimedean-property.png", - "infinite-cartesian-product.png" + "infinite-cartesian-product.png", + "abs-value-geom.png", + "triangle-inequality.png", + "triangle-inequality-degenerate.png", + "adj-list-representation.png", + "adj-matrix-representation.png" ], "File Hashes": { "algorithms/index.md": "3ac071354e55242919cc574eb43de6f8", @@ -380,7 +385,7 @@ "set/index.md": "91060cf5e604f7683a34710dda2ea10b", "set/graphs.md": "15aa43bf7f73347219f822e4b400e9bf", "_journal/2024-03-19.md": "a0807691819725bf44c0262405e97cbb", - "_journal/2024-03/2024-03-18.md": "63c3c843fc6cfc2cd289ac8b7b108391", + "_journal/2024-03/2024-03-18.md": "2c711c50247a9880f7ed0d33b16e1101", "awk/variables.md": "e40a20545358228319f789243d8b9f77", "awk/regexp.md": "4ce38103575a5321a1503b28e1d714dd", "awk/index.md": "257738d2d864933fb4bd21e8609c525d", @@ -398,7 +403,7 @@ "x86-64/declarations.md": "75bc7857cf2207a40cd7f0ee056af2f2", "x86-64/instructions.md": "06b7fbe1a7a9568b80239310eb72e87a", "git/refs.md": "e20c2c9b14ba6c2bd235416017c5c474", - "set/trees.md": "f5c6cd3bf1834b84fb0a55114a9c80f6", + "set/trees.md": "495fb5f29b20fbee9812cee2ea9e4504", "_journal/2024-03-24.md": "1974cdb9fc42c3a8bebb8ac76d4b1fd6", "_journal/2024-03/2024-03-23.md": "ad4e92cc2bf37f174a0758a0753bf69b", "_journal/2024-03/2024-03-22.md": "a509066c9cd2df692549e89f241d7bd9", @@ -503,7 +508,7 @@ "programming/pred-trans.md": "c02471c6c9728dd19f8df7bc180ef8b1", "set/axioms.md": "063955bf19c703e9ad23be2aee4f1ab7", "_journal/2024-05-14.md": "f6ece1d6c178d57875786f87345343c5", - "_journal/2024-05/2024-05-13.md": "71eb7924653eed5b6abd84d3a13b532b", + "_journal/2024-05/2024-05-13.md": "d549dd75fb42b4280d4914781edb0113", "x86-64/registers.md": "5cb49ae47fb0f95df6e15991274f4ad3", "_journal/2024-05-15.md": "4e6a7e6df32e93f0d8a56bc76613d908", "_journal/2024-05/2024-05-14.md": "f6ece1d6c178d57875786f87345343c5", @@ -766,7 +771,7 @@ "_journal/2024-08/2024-08-21.md": "1637b8ec8475cf3eb4f41d1d86cbf5df", "_journal/2024-08/2024-08-20.md": "e8bec308d1b29e411c6799ace7ef6571", "_journal/2024-08-23.md": "3b2feab2cc927e267263cb1e9c173d50", - "set/natural-numbers.md": "97ca466daf1173ed8973db1d1a1935cc", + "set/natural-numbers.md": "0646f917887830a8108bb8bcdfcff770", "_journal/2024-08-24.md": "563fad24740e44734a87d7c3ec46cec4", "_journal/2024-08/2024-08-23.md": "7b5a40e83d8f07ff54cd9708017d029c", "_journal/2024-08/2024-08-22.md": "050235d5dc772b542773743b57ce3afe", @@ -779,7 +784,10 @@ "c17/types/derived.md": "aff0d2b6d218fb67af3cc92ead924de3", "c17/types/basic.md": "5064e21e683c0218890058882e06b6f3", "c17/types/index.md": "b3e4f47b5f1f2a76d1d039e6263a41b8", - "_journal/2024-08-25.md": "316dcc41923e7c043bee51f434c90c85" + "_journal/2024-08-25.md": "e73a8edbd027d0f1a39289540eb512f2", + "_journal/2024-08/2024-08-24.md": "563fad24740e44734a87d7c3ec46cec4", + "algebra/abs-val.md": "a47bc08db62304eb526d15ede3e300cf", + "data-structures/graphs.md": "594d136ce637448641631c3647599c3a" }, "fields_dict": { "Basic": [ diff --git a/notes/_journal/2024-03/2024-03-18.md b/notes/_journal/2024-03/2024-03-18.md index a1bd73b..8e292fd 100644 --- a/notes/_journal/2024-03/2024-03-18.md +++ b/notes/_journal/2024-03/2024-03-18.md @@ -11,6 +11,6 @@ title: "2024-03-18" - [ ] Log Work Hours (Max 3 hours) * Finished [buffer pool manager project](https://15445.courses.cs.cmu.edu/fall2022/project1/). -* Added notes on [[graphs|graph]]-related terminology. Updated "Introduction to Algorithms" to fourth edition. +* Added notes on [[set/graphs|graph]]-related terminology. Updated "Introduction to Algorithms" to fourth edition. * Watched [How My Student Became 1 Dan](https://www.youtube.com/watch?v=ZvHL_lwfYYI&t=595s). * Reviewed and commented on Gus's latest pass of soft skills course. \ No newline at end of file diff --git a/notes/_journal/2024-05/2024-05-13.md b/notes/_journal/2024-05/2024-05-13.md index 3ea1a1f..b1b3d93 100644 --- a/notes/_journal/2024-05/2024-05-13.md +++ b/notes/_journal/2024-05/2024-05-13.md @@ -8,7 +8,7 @@ title: "2024-05-13" - [ ] Go (1 Life & Death Problem) - [ ] Korean (Read 1 Story) -* Notes on [[graphs#Subgraphs|subgraphs]] and induced subgraphs. +* Notes on [[set/graphs#Subgraphs|subgraphs]] and induced subgraphs. * Notes on [[remotes]]. * Read through chapter 7 of "The Science of Programming", touching on the $wp$ predicate transformer. * Read chapter 1 of "Elements of Set Theory". Made some progress on chapter 2 which touches on the basic axiomatic foundations. \ No newline at end of file diff --git a/notes/_journal/2024-08-25.md b/notes/_journal/2024-08-25.md index b413e3b..3afa679 100644 --- a/notes/_journal/2024-08-25.md +++ b/notes/_journal/2024-08-25.md @@ -6,4 +6,7 @@ title: "2024-08-25" - [x] KoL - [x] OGS - [ ] Sheet Music (10 min.) -- [ ] Korean (Read 1 Story) \ No newline at end of file +- [ ] Korean (Read 1 Story) + +* Standard [[data-structures/graphs|graph]] representations. +* [[abs-val|Absolute value]] and the [[abs-val#Triangle Inequality|triangle inequality]]. \ No newline at end of file diff --git a/notes/_journal/2024-08-24.md b/notes/_journal/2024-08/2024-08-24.md similarity index 100% rename from notes/_journal/2024-08-24.md rename to notes/_journal/2024-08/2024-08-24.md diff --git a/notes/algebra/abs-val.md b/notes/algebra/abs-val.md new file mode 100644 index 0000000..eae9d5c --- /dev/null +++ b/notes/algebra/abs-val.md @@ -0,0 +1,160 @@ +--- +title: Absolute Value +TARGET DECK: Obsidian::STEM +FILE TAGS: algebra::abs +tags: + - algebra +--- + +## Overview + +Let $x \in \mathbb{R}$. The **absolute value** of $x$, denoted $\lvert x \rvert$, is defined as $$\lvert x \rvert = \begin{cases} x & \text{if } x \geq 0 \\ -x & \text{if } x \leq 0 \end{cases}$$ + +%%ANKI +Basic +How is the absolute value of $x \in \mathbb{R}$ denoted? +Back: $\lvert x \rvert$ +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +How is the absolute value of $x \in \mathbb{R}$ defined? +Back: $\lvert x \rvert = \begin{cases} x & \text{if } x \geq 0 \\ -x & \text{if } x \leq 0 \end{cases}$ +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +The absolute value of $x \in \mathbb{R}$ considers what two cases? +Back: Whether $x \geq 0$ or $x \leq 0$. +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x \in \mathbb{R}$. When is $-\lvert x \rvert \leq x < \lvert x \rvert$? +Back: When $x < 0$. +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x \in \mathbb{R}$. When is $-\lvert x \rvert < x \leq \lvert x \rvert$? +Back: When $x > 0$. +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x \in \mathbb{R}$. When is $-\lvert x \rvert \leq x \leq \lvert x \rvert$? +Back: Always. +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x, a \in \mathbb{R}$ and $a \geq 0$. How is $\lvert x \rvert \leq a$ equivalently written as a chain of inequalities? +Back: $-a \leq x \leq a$ +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x, a \in \mathbb{R}$ and $a \geq 0$. How is $\lvert x \rvert \leq a$ geometricaly depicted? +Back: +![[abs-value-geom.png]] +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x, a \in \mathbb{R}$ and $a \geq 0$. How is $-a \leq x \leq a$ equivalently written using absolute value? +Back: $\lvert x \rvert \leq a$ +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Let $x, a \in \mathbb{R}$ and $a \geq 0$. How is $-a \leq x \leq a$ geometrically depicted? +Back: +![[abs-value-geom.png]] +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +## Triangle Inequality + +Let $x, y \in \mathbb{R}$. Then the **triangle inequality** of $\mathbb{R}$ states $$\lvert x + y \rvert \leq \lvert x \rvert + \lvert y \rvert$$ + +%%ANKI +Basic +What does the triangle inequality of $\mathbb{R}$ state? +Back: For $x, y \in \mathbb{R}$, $\lvert x + y \rvert \leq \lvert x \rvert + \lvert y \rvert$. +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +Why is the triangle inequality named the way it is? +Back: The length of a triangle side is $\leq$ the sum of the other two sides. +Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). + +END%% + +%%ANKI +Basic +What algebraic inequality is demonstrated in the following? +![[triangle-inequality.png]] +Back: The triangle inequality of $\mathbb{R}$. +Reference: “Triangle Inequality.” In _Wikipedia_, July 1, 2024. [https://en.wikipedia.org/w/index.php?title=Triangle_inequality](https://en.wikipedia.org/w/index.php?title=Triangle_inequality&oldid=1232015318). + +END%% + +%%ANKI +Basic +What degenerate triangle justifies use of $\leq$ over $<$ in the triangle inequality of $\mathbb{R}$? +Back: +![[triangle-inequality-degenerate.png]] +Reference: “Triangle Inequality.” In _Wikipedia_, July 1, 2024. [https://en.wikipedia.org/w/index.php?title=Triangle_inequality](https://en.wikipedia.org/w/index.php?title=Triangle_inequality&oldid=1232015318). + +END%% + +%%ANKI +Basic +What two chains of inequalities can be added together to prove the triangle inequality of $\mathbb{R}$? +Back: $-\lvert x \rvert \leq x \leq \lvert x \rvert$ and $-\lvert y \rvert \leq y \leq \lvert y \rvert$. +Reference: “Triangle Inequality.” In _Wikipedia_, July 1, 2024. [https://en.wikipedia.org/w/index.php?title=Triangle_inequality](https://en.wikipedia.org/w/index.php?title=Triangle_inequality&oldid=1232015318). + +END%% + +%%ANKI +Basic +What does the general triangle inequality of $\mathbb{R}$ state? +Back: For real numbers $a_1, \ldots, a_n$, $$\left\lvert \sum_{k=1}^n a_k \right\rvert \leq \sum_{k=1}^n \lvert a_k \rvert$$ +Reference: “Triangle Inequality.” In _Wikipedia_, July 1, 2024. [https://en.wikipedia.org/w/index.php?title=Triangle_inequality](https://en.wikipedia.org/w/index.php?title=Triangle_inequality&oldid=1232015318). + +END%% + +%%ANKI +Basic +Let $a_1\, \ldots, a_n \in \mathbb{R}$. What is the following a generalization of? $$\left\lvert \sum_{k=1}^n a_k \right\rvert \leq \sum_{k=1}^n \lvert a_k \rvert$$ +Back: The triangle inequality of $\mathbb{R}$. +Reference: “Triangle Inequality.” In _Wikipedia_, July 1, 2024. [https://en.wikipedia.org/w/index.php?title=Triangle_inequality](https://en.wikipedia.org/w/index.php?title=Triangle_inequality&oldid=1232015318). + +END%% + +## Bibliography + +* Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980). +* “Triangle Inequality.” In _Wikipedia_, July 1, 2024. [https://en.wikipedia.org/w/index.php?title=Triangle_inequality](https://en.wikipedia.org/w/index.php?title=Triangle_inequality&oldid=1232015318). \ No newline at end of file diff --git a/notes/algebra/images/abs-value-geom.png b/notes/algebra/images/abs-value-geom.png new file mode 100644 index 0000000..4230bf2 Binary files /dev/null and b/notes/algebra/images/abs-value-geom.png differ diff --git a/notes/algebra/images/triangle-inequality-degenerate.png b/notes/algebra/images/triangle-inequality-degenerate.png new file mode 100644 index 0000000..1145d27 Binary files /dev/null and b/notes/algebra/images/triangle-inequality-degenerate.png differ diff --git a/notes/algebra/images/triangle-inequality.png b/notes/algebra/images/triangle-inequality.png new file mode 100644 index 0000000..29739f8 Binary files /dev/null and b/notes/algebra/images/triangle-inequality.png differ diff --git a/notes/data-structures/graphs.md b/notes/data-structures/graphs.md new file mode 100644 index 0000000..335b99f --- /dev/null +++ b/notes/data-structures/graphs.md @@ -0,0 +1,194 @@ +--- +title: Graphs +TARGET DECK: Obsidian::STEM +FILE TAGS: data_structure::graph +tags: + - data_structure + - graph +--- + +## Overview + +There are two standard ways of representing graphs in memory: **adjacency-list** representations and **adjacency-matrix** representations. + +%%ANKI +Basic +Using asymptotic notation, how do the number of edges in a graph relate to the number of vertices? +Back: $\lvert E \rvert = O(\lvert V^2 \rvert)$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +For graph $G = \langle V, E \rangle$, *why* is $\lvert E \rvert = O(\lvert V^2 \rvert)$? +Back: Because $E$ is a binary relation on $V$. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +What are the two standard ways of representing graphs in memory? +Back: The adjacency-list and adjacency-matrix representation. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Which standard graph representation is preferred for sparse graphs? +Back: Adjacency-list representations. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Which standard graph representation is preferred for dense graphs? +Back: Adjacency-matrix representations. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +When is a graph $G = \langle V, E \rangle$ considered dense? +Back: When $\lvert E \rvert \approx \lvert V \rvert^2$. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +## Adjacency-List + +Let $G = \langle V, E \rangle$ be a graph. An adjacency-list representation of $G$ has an array of size $\lvert V \rvert$. Given $v \in V$, the index corresponding to $v$ contains a linked list containing all adjacent vertices. + +%%ANKI +Basic +Let $G = \langle V, E \rangle$ be a graph. It's adjacency-list representation is an array of what size? +Back: $\lvert V \rvert$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +The following is an example of what kind of graph representation? +![[adj-list-representation.png]] +Back: An adjacency-list representation. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Are adjacency-list representations used for directed or undirected graphs? +Back: Both. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Let $G = \langle V, E \rangle$ be a graph. What is the sum of its adjacency-list representation's list lengths? +Back: N/A. This depends on whether $G$ is a directed or undirected graph. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Let $G = \langle V, E \rangle$ be a digraph. What is the sum of its adjacency-list representation's list lengths? +Back: $\lvert E \rvert$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Let $G = \langle V, E \rangle$ be an undirected graph. What is the sum of its adjacency-list representation's list lengths? +Back: $2\lvert E \rvert$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Which lemma explains the sum of an undirected graph adjacency-list representation's list lengths? +Back: The handshake lemma. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Let $G = \langle V, E \rangle$. What is the memory usage of its adjacency-list representation? +Back: $\Theta(\lvert V \rvert + \lvert E \rvert)$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +## Adjacency-Matrix + +Let $G = \langle V, E \rangle$ be a graph. An adjacency-matrix representation of $G$ is a $\lvert V \rvert \times \lvert V \rvert$ matrix $A = (a_{ij})$ such that $$a_{ij} = \begin{cases} 1 & \text{if } \langle i, j \rangle \in E \\ 0 & \text{otherwise} \end{cases}$$ + +%%ANKI +Basic +Let $G = \langle V, E \rangle$ be a graph. It's adjacency-matrix representation is a matrix of what dimensions? +Back: $\lvert V \rvert \times \lvert V \rvert$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +What values are found in an adjacency-matrix representation of a graph? +Back: $0$ and/or $1$. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +The following is an example of what kind of graph representation? +![[adj-matrix-representation.png]] +Back: An adjacency-matrix representation. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Are adjacency-matrix representations used for directed or undirected graphs? +Back: Both. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +For what graphs are adjacency-matrix representations symmetric along its diagonal? +Back: Undirected graphs. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +*Why* is the adjacency-matrix representation of undirected graph $G = \langle V, E \rangle$ symmetric along its diagonal? +Back: If $\langle i, j \rangle \in E$ then $\langle j, i \rangle \in E$. +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +%%ANKI +Basic +Let $G = \langle V, E \rangle$. What is the memory usage of its adjacency-matrix representation? +Back: $\Theta(\lvert V \rvert^2)$ +Reference: Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). + +END%% + +## Bibliography + +* Thomas H. Cormen et al., _Introduction to Algorithms_, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022). \ No newline at end of file diff --git a/notes/data-structures/images/adj-list-representation.png b/notes/data-structures/images/adj-list-representation.png new file mode 100644 index 0000000..5d4d0cd Binary files /dev/null and b/notes/data-structures/images/adj-list-representation.png differ diff --git a/notes/data-structures/images/adj-matrix-representation.png b/notes/data-structures/images/adj-matrix-representation.png new file mode 100644 index 0000000..5a041a6 Binary files /dev/null and b/notes/data-structures/images/adj-matrix-representation.png differ diff --git a/notes/set/natural-numbers.md b/notes/set/natural-numbers.md index 0b72338..39805c7 100644 --- a/notes/set/natural-numbers.md +++ b/notes/set/natural-numbers.md @@ -257,6 +257,14 @@ Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Pre END%% +%%ANKI +Basic +In set theory, $\omega$ denotes what set? +Back: The natural numbers. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + %%ANKI Basic What is the smallest inductive set? @@ -281,6 +289,86 @@ Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Pre END%% +%%ANKI +Basic +What can be said about a subset of $\omega$? +Back: N/A. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +What can be said about an inductive subset of $\omega$? +Back: It must coincide with $\omega$. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +Why must every inductive subset of $\omega$ coincide with $\omega$? +Back: Because $\omega$ is the smallest inductive set. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +What does the induction principle for $\omega$ state? +Back: Every inductive subset of $\omega$ coincides with $\omega$. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +What name is given to the principle, "every inductive subset of $\omega$ coincides with $\omega$?" +Back: The induction principle for $\omega$. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +Inductive sets correspond to what kind of proof method? +Back: Proof by induction. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +Prove $P(n)$ is true for all $n \in \mathbb{N}$ using induction. What set do we prove is inductive? +Back: $\{n \in \mathbb{N} \mid P(n)\}$ +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +*How* are inductive sets and proof by induction related? +Back: An induction proof corresponds to proving a related set is inductive. +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +What inductive set do we construct to prove the following by induction? $$\text{Every natural number is nonnegative}$$ +Back: $\{n \in \omega \mid 0 \leq n\}$ +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + +%%ANKI +Basic +What inductive set do we construct to prove the following by induction? $$\text{Every nonzero natural number is the successor of another natural number}$$ +Back: $\{n \in \omega \mid n = 0 \lor (\exists m \in \omega, n = m^+)\}$ +Reference: Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). + +END%% + ## Bibliography * Herbert B. Enderton, *Elements of Set Theory* (New York: Academic Press, 1977). \ No newline at end of file diff --git a/notes/set/trees.md b/notes/set/trees.md index 032ff08..6bdfb62 100644 --- a/notes/set/trees.md +++ b/notes/set/trees.md @@ -10,7 +10,7 @@ tags: ## Overview -A **free tree** is a connected, acyclic, undirected [[graphs|graph]]. If an undirected graph is acyclic but possibly disconnected, it is a **forest**. +A **free tree** is a connected, acyclic, undirected [[set/graphs|graph]]. If an undirected graph is acyclic but possibly disconnected, it is a **forest**. %%ANKI Basic @@ -126,7 +126,7 @@ END%% A **rooted tree** is a free tree in which one vertex is distinguished/blessed as the **root**. We call vertices of rooted trees **nodes**. -Let $T$ be a rooted tree with root $r$. Any node $y$ on the [[graphs#Paths|path]] from $r$ to node $x$ is an **ancestor** of $x$. Likewise, $x$ is a **descendant** of $y$. If the last edge on the path from $r$ to $x$ is $\{y, x\}$, $y$ is the **parent** of $x$ and $x$ is a **child** of $y$. Nodes with the same parent are called **siblings**. +Let $T$ be a rooted tree with root $r$. Any node $y$ on the [[set/graphs#Paths|path]] from $r$ to node $x$ is an **ancestor** of $x$. Likewise, $x$ is a **descendant** of $y$. If the last edge on the path from $r$ to $x$ is $\{y, x\}$, $y$ is the **parent** of $x$ and $x$ is a **child** of $y$. Nodes with the same parent are called **siblings**. A node with no children is an **external node** or **leaf**. A node with at least one child is an **internal node** or **nonleaf**. The number of children of a node is the **degree** of said node. The length of the path from the root to a node $x$ is the **depth** of $x$ in $T$. A **level** of a tree consists of all nodes at the same depth. The **height** of a node in a tree is the length of the longest path from the node to a leaf.