Algorithms, Complexity, and CS Notation in LaTeX - LaTeX Cloud Studio Documentation

This guide covers the broader computer-science notation stack in LaTeX: algorithms, graph notation, asymptotic complexity, and related mathematical symbols.

Looking for pseudocode? Use the focused LaTeX pseudocode guide for algorithm, algorithmicx, and algpseudocode examples.

Essential Algorithm Packages

\usepackage{algorithm}      % Algorithm environment
\usepackage{algorithmicx}   % Extended algorithmic commands
\usepackage{algpseudocode}  % Pseudocode style
\usepackage{listings}       % Code listings
\usepackage{clrscode3e}     % CLRS book style
\usepackage{complexity}     % Complexity classes
\usepackage{amsmath}        % Mathematical notation

Basic Pseudocode

Simple Algorithm Structure

\begin{algorithm}
\caption{Binary Search}
\begin{algorithmic}[1]
\Procedure{BinarySearch}{$A, n, x$}
    \State $\textit{left} \gets 1$
    \State $\textit{right} \gets n$
    \While{$\textit{left} \leq \textit{right}$}
        \State $\textit{mid} \gets \lfloor (\textit{left} + \textit{right})/2 \rfloor$
        \If{$A[\textit{mid}] = x$}
            \State \textbf{return} $\textit{mid}$
        \ElsIf{$A[\textit{mid}] < x$}
            \State $\textit{left} \gets \textit{mid} + 1$
        \Else
            \State $\textit{right} \gets \textit{mid} - 1$
        \EndIf
    \EndWhile
    \State \textbf{return} $\textit{null}$
\EndProcedure
\end{algorithmic}
\end{algorithm}

Control Structures

\begin{algorithmic}[1]
\State $x \gets 0$

\If{condition}
    \State statement
\ElsIf{other condition}
    \State other statement
\Else
    \State default statement
\EndIf

\While{condition}
    \State loop body
\EndWhile

\For{$i = 1$ \textbf{to} $n$}
    \State loop body
\EndFor

\For{\textbf{each} $item$ \textbf{in} $collection$}
    \State process item
\EndFor

\Repeat
    \State loop body
\Until{condition}

Rendered Output

The algorithmicx package produces formatted pseudocode with proper indentation:\State produces a simple statement line\If{condition} produces: if condition then\For{$i = 1$ \textbf{to} $n$} produces: for

i = 1

n

Sorting Algorithms

Merge Sort

\begin{algorithm}
\caption{Merge Sort}
\begin{algorithmic}[1]
\Procedure{MergeSort}{$A, p, r$}
    \If{$p < r$}
        \State $q \gets \lfloor (p + r)/2 \rfloor$
        \State \Call{MergeSort}{$A, p, q$}
        \State \Call{MergeSort}{$A, q+1, r$}
        \State \Call{Merge}{$A, p, q, r$}
    \EndIf
\EndProcedure

\Procedure{Merge}{$A, p, q, r$}
    \State $n_1 \gets q - p + 1$
    \State $n_2 \gets r - q$
    \State Create arrays $L[1..n_1+1]$ and $R[1..n_2+1]$
    \For{$i = 1$ \textbf{to} $n_1$}
        \State $L[i] \gets A[p + i - 1]$
    \EndFor
    \For{$j = 1$ \textbf{to} $n_2$}
        \State $R[j] \gets A[q + j]$
    \EndFor
    \State $L[n_1 + 1] \gets \infty$
    \State $R[n_2 + 1] \gets \infty$
    \State $i \gets 1$, $j \gets 1$
    \For{$k = p$ \textbf{to} $r$}
        \If{$L[i] \leq R[j]$}
            \State $A[k] \gets L[i]$
            \State $i \gets i + 1$
        \Else
            \State $A[k] \gets R[j]$
            \State $j \gets j + 1$
        \EndIf
    \EndFor
\EndProcedure
\end{algorithmic}
\end{algorithm}

Graph Algorithms

Depth-First Search

\begin{algorithm}
\caption{Depth-First Search}
\begin{algorithmic}[1]
\Procedure{DFS}{$G$}
    \For{\textbf{each} vertex $u \in V[G]$}
        \State $color[u] \gets \text{WHITE}$
        \State $\pi[u] \gets \text{NIL}$
    \EndFor
    \State $time \gets 0$
    \For{\textbf{each} vertex $u \in V[G]$}
        \If{$color[u] = \text{WHITE}$}
            \State \Call{DFS-Visit}{$u$}
        \EndIf
    \EndFor
\EndProcedure

\Procedure{DFS-Visit}{$u$}
    \State $color[u] \gets \text{GRAY}$
    \State $time \gets time + 1$
    \State $d[u] \gets time$
    \For{\textbf{each} $v \in Adj[u]$}
        \If{$color[v] = \text{WHITE}$}
            \State $\pi[v] \gets u$
            \State \Call{DFS-Visit}{$v$}
        \EndIf
    \EndFor
    \State $color[u] \gets \text{BLACK}$
    \State $time \gets time + 1$
    \State $f[u] \gets time$
\EndProcedure
\end{algorithmic}
\end{algorithm}

Dijkstra’s Algorithm

\begin{algorithm}
\caption{Dijkstra's Shortest Path}
\begin{algorithmic}[1]
\Procedure{Dijkstra}{$G, w, s$}
    \State \Call{Initialize-Single-Source}{$G, s$}
    \State $S \gets \emptyset$
    \State $Q \gets V[G]$
    \While{$Q \neq \emptyset$}
        \State $u \gets \Call{Extract-Min}{Q}$
        \State $S \gets S \cup \{u\}$
        \For{\textbf{each} vertex $v \in Adj[u]$}
            \State \Call{Relax}{$u, v, w$}
        \EndFor
    \EndWhile
\EndProcedure

\Procedure{Relax}{$u, v, w$}
    \If{$d[v] > d[u] + w(u,v)$}
        \State $d[v] \gets d[u] + w(u,v)$
        \State $\pi[v] \gets u$
    \EndIf
\EndProcedure
\end{algorithmic}
\end{algorithm}

Complexity Analysis

Big O Notation

% Time complexities
$O(1)$ \quad\text{constant time}
$O(\log n)$ \quad\text{logarithmic time}
$O(n)$ \quad\text{linear time}
$O(n \log n)$ \quad\text{linearithmic time}
$O(n^2)$ \quad\text{quadratic time}
$O(n^3)$ \quad\text{cubic time}
$O(2^n)$ \quad\text{exponential time}
$O(n!)$ \quad\text{factorial time}

% Space complexities
$O(1)$ \quad\text{constant space}
$O(n)$ \quad\text{linear space}
$O(n^2)$ \quad\text{quadratic space}

% Asymptotic notation
$f(n) = O(g(n))$ \quad\text{upper bound}
$f(n) = \Omega(g(n))$ \quad\text{lower bound}
$f(n) = \Theta(g(n))$ \quad\text{tight bound}
$f(n) = o(g(n))$ \quad\text{strict upper bound}
$f(n) = \omega(g(n))$ \quad\text{strict lower bound}

Complexity Classes

% Using complexity package
\P \quad\text{Polynomial time}
\NP \quad\text{Nondeterministic polynomial time}
\coNP \quad\text{Co-NP}
\PSPACE \quad\text{Polynomial space}
\EXPTIME \quad\text{Exponential time}
\NEXPTIME \quad\text{Nondeterministic exponential time}

% Reductions
$A \leq_p B$ \quad\text{polynomial-time reduction}
$A \leq_m B$ \quad\text{many-one reduction}

% Completeness
$L$ is $\NP$-complete if:
\begin{enumerate}
    \item $L \in \NP$
    \item For every $L' \in \NP$, $L' \leq_p L$
\end{enumerate}

Data Structures

Binary Search Tree Operations

\begin{algorithm}
\caption{Binary Search Tree Insert}
\begin{algorithmic}[1]
\Procedure{Tree-Insert}{$T, z$}
    \State $y \gets \text{NIL}$
    \State $x \gets root[T]$
    \While{$x \neq \text{NIL}$}
        \State $y \gets x$
        \If{$key[z] < key[x]$}
            \State $x \gets left[x]$
        \Else
            \State $x \gets right[x]$
        \EndIf
    \EndWhile
    \State $p[z] \gets y$
    \If{$y = \text{NIL}$}
        \State $root[T] \gets z$
    \ElsIf{$key[z] < key[y]$}
        \State $left[y] \gets z$
    \Else
        \State $right[y] \gets z$
    \EndIf
\EndProcedure
\end{algorithmic}
\end{algorithm}

Hash Table Operations

\begin{algorithm}
\caption{Hash Table with Chaining}
\begin{algorithmic}[1]
\Procedure{Chained-Hash-Insert}{$T, x$}
    \State Insert $x$ at head of list $T[h(key[x])]$
\EndProcedure

\Procedure{Chained-Hash-Search}{$T, k$}
    \State Search for element with key $k$ in list $T[h(k)]$
\EndProcedure

\Procedure{Chained-Hash-Delete}{$T, x$}
    \State Delete $x$ from list $T[h(key[x])]$
\EndProcedure

\Function{Hash-Function}{$k, m$}
    \State \textbf{return} $k \bmod m$
\EndFunction

Dynamic Programming

Longest Common Subsequence

\begin{algorithm}
\caption{Longest Common Subsequence}
\begin{algorithmic}[1]
\Procedure{LCS-Length}{$X, Y$}
    \State $m \gets length[X]$
    \State $n \gets length[Y]$
    \For{$i = 1$ \textbf{to} $m$}
        \State $c[i,0] \gets 0$
    \EndFor
    \For{$j = 0$ \textbf{to} $n$}
        \State $c[0,j] \gets 0$
    \EndFor
    \For{$i = 1$ \textbf{to} $m$}
        \For{$j = 1$ \textbf{to} $n$}
            \If{$x_i = y_j$}
                \State $c[i,j] \gets c[i-1,j-1] + 1$
                \State $b[i,j] \gets$ "↖"
            \ElsIf{$c[i-1,j] \geq c[i,j-1]$}
                \State $c[i,j] \gets c[i-1,j]$
                \State $b[i,j] \gets$ "↑"
            \Else
                \State $c[i,j] \gets c[i,j-1]$
                \State $b[i,j] \gets$ "←"
            \EndIf
        \EndFor
    \EndFor
    \State \textbf{return} $c$ and $b$
\EndProcedure
\end{algorithmic}
\end{algorithm}

Mathematical Algorithms

Euclidean Algorithm

\begin{algorithm}
\caption{Euclidean Algorithm}
\begin{algorithmic}[1]
\Function{GCD}{$a, b$}
    \While{$b \neq 0$}
        \State $temp \gets b$
        \State $b \gets a \bmod b$
        \State $a \gets temp$
    \EndWhile
    \State \textbf{return} $a$
\EndFunction

\Function{Extended-GCD}{$a, b$}
    \If{$b = 0$}
        \State \textbf{return} $(a, 1, 0)$
    \Else
        \State $(d, x', y') \gets \Call{Extended-GCD}{b, a \bmod b}$
        \State $x \gets y'$
        \State $y \gets x' - \lfloor a/b \rfloor \cdot y'$
        \State \textbf{return} $(d, x, y)$
    \EndIf
\EndFunction
\end{algorithmic}
\end{algorithm}

Machine Learning Algorithms

Gradient Descent

\begin{algorithm}
\caption{Gradient Descent}
\begin{algorithmic}[1]
\Procedure{Gradient-Descent}{$f, \nabla f, \alpha, \epsilon$}
    \State Initialize $\mathbf{x}_0$
    \State $k \gets 0$
    \Repeat
        \State $\mathbf{g}_k \gets \nabla f(\mathbf{x}_k)$
        \State $\mathbf{x}_{k+1} \gets \mathbf{x}_k - \alpha \mathbf{g}_k$
        \State $k \gets k + 1$
    \Until{$\|\mathbf{g}_k\| < \epsilon$}
    \State \textbf{return} $\mathbf{x}_k$
\EndProcedure

\Function{Learning-Rate-Schedule}{$k$}
    \State \textbf{return} $\frac{\alpha_0}{1 + \beta k}$
\EndFunction
\end{algorithmic}
\end{algorithm}

Parallel Algorithms

Parallel Merge Sort

\begin{algorithm}
\caption{Parallel Merge Sort}
\begin{algorithmic}[1]
\Procedure{P-Merge-Sort}{$A, p, r$}
    \If{$p < r$}
        \State $q \gets \lfloor (p + r)/2 \rfloor$
        \State \textbf{spawn} \Call{P-Merge-Sort}{$A, p, q$}
        \State \Call{P-Merge-Sort}{$A, q+1, r$}
        \State \textbf{sync}
        \State \Call{P-Merge}{$A, p, q, r$}
    \EndIf
\EndProcedure

\Procedure{P-Merge}{$A, p, q, r$}
    \State $n_1 \gets q - p + 1$
    \State $n_2 \gets r - q$
    \If{$n_1 < n_2$}
        \State Exchange $p \leftrightarrow q+1$ and $n_1 \leftrightarrow n_2$
    \EndIf
    \If{$n_1 = 0$}
        \State \textbf{return}
    \Else
        \State $q' \gets \lfloor (p + q)/2 \rfloor$
        \State $r' \gets \Call{Binary-Search}{A[q'], A, q+1, r}$
        \State $s \gets p + (q' - p) + (r' - (q+1))$
        \State $A'[s] \gets A[q']$
        \State \textbf{spawn} \Call{P-Merge}{A, p, q'-1, r'-1}
        \State \Call{P-Merge}{A, q'+1, q, r'+1}
        \State \textbf{sync}
    \EndIf
\EndProcedure
\end{algorithmic}
\end{algorithm}

Recurrence Relations

Solving Recurrences

% Master Theorem
\textbf{Master Theorem:} Let $T(n) = aT(n/b) + f(n)$ where $a \geq 1$ and $b > 1$.

\textbf{Case 1:} If $f(n) = O(n^{\log_b a - \epsilon})$ for some $\epsilon > 0$,
then $T(n) = \Theta(n^{\log_b a})$.

\textbf{Case 2:} If $f(n) = \Theta(n^{\log_b a})$,
then $T(n) = \Theta(n^{\log_b a} \log n)$.

\textbf{Case 3:} If $f(n) = \Omega(n^{\log_b a + \epsilon})$ for some $\epsilon > 0$,
and $af(n/b) \leq cf(n)$ for some $c < 1$ and sufficiently large $n$,
then $T(n) = \Theta(f(n))$.

% Examples
$T(n) = 2T(n/2) + n$ \quad $\Rightarrow$ \quad $T(n) = \Theta(n \log n)$
$T(n) = 3T(n/4) + n^2$ \quad $\Rightarrow$ \quad $T(n) = \Theta(n^2)$
$T(n) = T(n-1) + 1$ \quad $\Rightarrow$ \quad $T(n) = \Theta(n)$

Algorithm Analysis Proofs

Correctness Proofs

% Loop invariant
\textbf{Loop Invariant for Insertion Sort:}

At the start of each iteration of the \textbf{for} loop of lines 1-8,
the subarray $A[1..j-1]$ consists of the elements originally in
$A[1..j-1]$, but in sorted order.

\textbf{Initialization:} Prior to the first iteration, when $j = 2$,
the subarray $A[1..j-1] = A[1..1] = \{A[1]\}$ is trivially sorted.

\textbf{Maintenance:} Assume the invariant holds at the beginning of an
iteration. The loop body moves $A[j-1], A[j-2], \ldots$ one position
to the right until it finds the proper position for $A[j]$.

\textbf{Termination:} When the loop terminates, $j = n + 1$. The
subarray $A[1..n]$ consists of the original elements in sorted order.

% Asymptotic proof
\textbf{Theorem:} For any function $f(n)$ and $g(n)$, 
$f(n) = O(g(n))$ if and only if there exist positive constants 
$c$ and $n_0$ such that $0 \leq f(n) \leq c \cdot g(n)$ 
for all $n \geq n_0$.

Best Practices

Clear Variable Names

Use descriptive variable names and consistent notation

Proper Indentation

Use consistent indentation to show algorithm structure

Complexity Analysis

Always include time and space complexity analysis

Invariants and Proofs

Document loop invariants and correctness proofs

Common Algorithm Notation

Notation	Meaning
←	Assignment
⊕	XOR operation
⊕	Addition in GF(2)
∀	For all
∃	There exists
∈	Element of
⊆	Subset of
∪	Union
∩	Intersection
∅	Empty set

Troubleshooting

Common issues:

Missing algorithm package: Install algorithm and algorithmicx
Line numbering: Use [1] option in algorithmic environment
Indentation problems: Check matching \If/\EndIf pairs
Symbol conflicts: Some symbols may conflict with math mode

Mathematics Notation

Mathematical expressions and notation

Creating Tables

Complexity comparison tables

Code Listings

Including actual code implementations

Physics Notation

Scientific computing applications

Documentation Index

​Essential Algorithm Packages

​Basic Pseudocode

​Simple Algorithm Structure

​Control Structures

Rendered Output

​Sorting Algorithms

​Merge Sort

​Graph Algorithms

​Depth-First Search

​Dijkstra’s Algorithm

​Complexity Analysis

​Big O Notation

​Complexity Classes

​Data Structures

​Binary Search Tree Operations

​Hash Table Operations

​Dynamic Programming

​Longest Common Subsequence

​Mathematical Algorithms

​Euclidean Algorithm

​Machine Learning Algorithms

​Gradient Descent

​Parallel Algorithms

​Parallel Merge Sort

​Recurrence Relations

​Solving Recurrences

​Algorithm Analysis Proofs

​Correctness Proofs

​Best Practices

Clear Variable Names

Proper Indentation

Complexity Analysis

Invariants and Proofs

​Common Algorithm Notation

​Troubleshooting

​Further Reading

Mathematics Notation

Creating Tables

Code Listings

Physics Notation

Essential Algorithm Packages

Basic Pseudocode

Simple Algorithm Structure

Control Structures

Sorting Algorithms

Merge Sort

Graph Algorithms

Depth-First Search

Dijkstra’s Algorithm

Complexity Analysis

Big O Notation

Complexity Classes

Data Structures

Binary Search Tree Operations

Hash Table Operations

Dynamic Programming

Longest Common Subsequence

Mathematical Algorithms

Euclidean Algorithm

Machine Learning Algorithms

Gradient Descent

Parallel Algorithms

Parallel Merge Sort

Recurrence Relations

Solving Recurrences

Algorithm Analysis Proofs

Correctness Proofs

Best Practices

Common Algorithm Notation

Troubleshooting

Further Reading