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Mathematical Algorithms

Mathematical Algorithms: A Rigorous Introduction

For Gifted High School Graduates

Introduction

Mathematics and computer science converge most elegantly in the study of algorithms—precise, step-by-step procedures for solving computational problems. This book bridges the gap between the intuitive problem-solving you’ve mastered in high school mathematics and the formal rigor demanded by advanced mathematical study and professional algorithm design.

As a gifted high school graduate, you likely possess strong mathematical intuition and have encountered algorithms in various forms: perhaps through contest mathematics, programming competitions, or advanced placement courses. However, the transition from computational facility to mathematical rigor represents a significant leap—one that distinguishes amateur problem-solving from professional mathematical thinking.

What Makes This Book Different

Most introductory algorithm texts assume either extensive programming background or advanced mathematical maturity. This book assumes neither, while respecting your intellectual capacity. We begin with fundamental concepts in discrete mathematics, formal logic, and proof techniques, then systematically build toward sophisticated algorithmic analysis. Every algorithm is presented with complete mathematical justification, from basic correctness proofs to detailed complexity analysis.

The “rigorous” in our title is not mere academic posturing. You will learn to think like a mathematician about computational problems: to state problems with precision, to prove correctness with logical certainty, and to analyze efficiency with mathematical exactness. This rigor serves a practical purpose—it provides the foundation for innovation in algorithm design and the confidence to tackle problems at the frontier of computer science.

Who Should Read This Book

This book is designed for exceptional high school graduates who are:

  • Comfortable with algebra, geometry, and basic calculus
  • Curious about the mathematical foundations of computer science
  • Planning to pursue quantitative fields in college or beyond
  • Interested in competition mathematics, programming contests, or research

You need not have extensive programming experience, though familiarity with basic programming concepts will prove helpful. More importantly, you should possess mathematical curiosity and the patience for careful reasoning.

How to Use This Book

Each chapter builds systematically on previous material. The early chapters establish mathematical foundations—set theory, logic, proof techniques, and basic combinatorics. These may seem removed from algorithms, but they provide the vocabulary and reasoning tools essential for everything that follows.

Exercises appear throughout each chapter, not merely at the end. These range from routine applications to challenging extensions that preview advanced topics. Work through them systematically; the ability to solve problems is the ultimate test of understanding.

Proofs appear in full detail, with explicit justification for each step. Initially, this may seem tedious, but this precision develops the mathematical maturity necessary for independent research. As you progress, you’ll internalize these patterns of reasoning and learn to construct your own rigorous arguments.

A Note on Mathematical Maturity

The transition from high school to university-level mathematics often proves challenging, even for talented students. High school mathematics emphasizes computation and application of known techniques. University mathematics demands abstract reasoning, formal proof, and comfort with ambiguity. This book serves as a bridge, introducing you to mathematical thinking through the concrete, intuitive domain of algorithms.

Expect to proceed slowly at first. Mathematical rigor cannot be rushed. Each concept must be thoroughly understood before moving forward, as later material builds inexorably on earlier foundations. The reward for this patience is genuine mathematical understanding—the ability to see not just what is true, but why it must be true.

The Journey Ahead

We begin with the fundamentals of mathematical reasoning and discrete structures, then progress through classical algorithms for sorting, searching, and graph problems. Later chapters explore more advanced topics: dynamic programming, network flows, and computational complexity. Throughout, we maintain our commitment to mathematical rigor while building intuition through carefully chosen examples and applications.

By the book’s conclusion, you will possess not merely a collection of algorithmic techniques, but a systematic framework for approaching computational problems with mathematical precision. You will understand not just how algorithms work, but why they work, when they work, and how to design new algorithms for novel problems.

This understanding will serve you well whether you pursue pure mathematics, computer science, engineering, or any field requiring quantitative reasoning. The habits of thought developed here—precision, rigor, and systematic analysis—transcend any particular application domain.

Welcome to the fascinating intersection of mathematics and computation. The journey requires dedication, but the destination rewards the effort with insights that will inform your thinking for years to come.

Table of Contents

  1. Foundations
  2. Mathematical Preliminaries
  3. Asymptotic Analysis
  4. Sorting Algorithms
  5. Searching Algorithms
  6. Graph Algorithms
  7. Dynamic Programming
  8. Advanced Topics

Foundations

What is an Algorithm?

An algorithm is a well-defined computational procedure that takes some value, or set of values, as input and produces some value, or set of values, as output. More formally:

Definition 1.1: An algorithm is a finite sequence of unambiguous instructions that, when executed with a given input, terminates and produces an output.

Properties of Algorithms

  1. Finiteness: An algorithm must terminate after a finite number of steps
  2. Definiteness: Each step must be precisely defined
  3. Input: Zero or more inputs from specified sets
  4. Output: One or more outputs with specified relation to inputs
  5. Effectiveness: All operations must be basic enough to be carried out exactly

Mathematical Preliminaries

Set Theory and Relations

Definition 2.1: A relation R on sets A and B is a subset of A × B.

Definition 2.2: A function f: A → B is a relation where for each a ∈ A, there exists exactly one b ∈ B such that (a,b) ∈ f.

Mathematical Induction

Theorem 2.1 (Principle of Mathematical Induction): Let P(n) be a predicate on positive integers. If:

  1. P(1) is true (base case)
  2. For all k ≥ 1, P(k) → P(k+1) (inductive step)

Then P(n) is true for all positive integers n.

Recurrence Relations

Definition 2.3: A recurrence relation is an equation that recursively defines a sequence where each term is defined as a function of preceding terms.

Example: The Fibonacci sequence: F(n) = F(n-1) + F(n-2) with F(0) = 0, F(1) = 1.


Asymptotic Analysis

Big-O Notation

Definition 3.1: For functions f(n) and g(n), we say f(n) = O(g(n)) if there exist positive constants c and n₀ such that: 0 ≤ f(n) ≤ cg(n) for all n ≥ n₀

Definition 3.2: f(n) = Ω(g(n)) if there exist positive constants c and n₀ such that: 0 ≤ cg(n) ≤ f(n) for all n ≥ n₀

Definition 3.3: f(n) = Θ(g(n)) if f(n) = O(g(n)) and f(n) = Ω(g(n))

Common Growth Rates

  1. Constant: Θ(1)
  2. Logarithmic: Θ(log n)
  3. Linear: Θ(n)
  4. Linearithmic: Θ(n log n)
  5. Quadratic: Θ(n²)
  6. Cubic: Θ(n³)
  7. Exponential: Θ(2ⁿ)
  8. Factorial: Θ(n!)

Sorting Algorithms

4.1 Selection Sort

The Big Idea: Imagine you’re organizing a deck of cards by repeatedly finding the smallest card and placing it at the front. Selection sort mimics this natural human sorting behavior.

Inspiration: This algorithm captures the essence of how we might sort physical objects - scan everything, pick the minimum, set it aside, repeat. It’s the most intuitive sorting method, making it perfect for understanding the fundamentals.

How it Works: In each pass, we find the minimum element in the unsorted portion and swap it with the first unsorted element. The sorted portion grows by one element each iteration, like building a wall brick by brick from left to right.

Problem: Given an array A[1..n] of n elements, sort them in non-decreasing order.

Algorithm 4.1: SELECTION-SORT(A)

SELECTION-SORT(A)
1 for i = 1 to n-1
2 min = i
3 for j = i+1 to n
4 if A[j] < A[min]
5 min = j
6 exchange A[i] with A[min]

Analysis:

  • Time Complexity: Θ(n²) in all cases
  • Space Complexity: Θ(1) auxiliary space
  • Invariant: At the start of each iteration, A[1..i-1] contains the i-1 smallest elements in sorted order

Theorem 4.1: SELECTION-SORT correctly sorts any array of n elements.

Proof: By loop invariant. The invariant holds initially (empty subarray is trivially sorted). If it holds before iteration i, then after iteration i, A[1..i] contains the i smallest elements in sorted order. When the loop terminates, A[1..n] is sorted. □

4.2 Insertion Sort

The Big Idea: Think of how you sort playing cards in your hand - you pick up each new card and slide it into its proper position among the cards you’ve already sorted.

Inspiration: This mirrors the natural way humans sort small collections. When you receive cards one by one, you don’t reshuffle everything; you just find where the new card belongs and insert it there.

How it Works: We build the sorted array one element at a time. For each new element, we “walk backwards” through the sorted portion, shifting elements until we find the correct insertion point. It’s like creating a perfectly ordered hand of cards.

Algorithm 4.2: INSERTION-SORT(A)

INSERTION-SORT(A)
1 for j = 2 to n
2 key = A[j]
3 i = j - 1
4 while i > 0 and A[i] > key
5 A[i+1] = A[i]
6 i = i - 1
7 A[i+1] = key

Analysis:

  • Best Case: Θ(n) - array already sorted
  • Worst Case: Θ(n²) - array reverse sorted
  • Average Case: Θ(n²)
  • Space Complexity: Θ(1)

Theorem 4.2: INSERTION-SORT correctly sorts any array of n elements.

4.3 Merge Sort

The Big Idea: “Divide and conquer” - split the problem in half, solve each half recursively, then cleverly combine the solutions. It’s like organizing two already-sorted piles of papers into one master pile.

Inspiration: Invented by John von Neumann in 1945, this algorithm embodies the mathematical principle that complex problems become manageable when broken into smaller, similar subproblems. It’s the sorting equivalent of “How do you eat an elephant? One bite at a time.”

How it Works: Recursively split the array until you have individual elements (trivially sorted), then merge pairs of sorted subarrays by comparing their front elements. The merging process is like shuffling two sorted decks into one perfectly ordered deck.

Algorithm 4.3: MERGE-SORT(A, p, r)

MERGE-SORT(A, p, r)
1 if p < r
2 q = ⌊(p+r)/2⌋
3 MERGE-SORT(A, p, q)
4 MERGE-SORT(A, q+1, r)
5 MERGE(A, p, q, r)

Algorithm 4.4: MERGE(A, p, q, r)

MERGE(A, p, q, r)
1 n₁ = q - p + 1
2 n₂ = r - q
3 let L[1..n₁+1] and R[1..n₂+1] be new arrays
4 for i = 1 to n₁
5 L[i] = A[p + i - 1]
6 for j = 1 to n₂
7 R[j] = A[q + j]
8 L[n₁+1] = ∞
9 R[n₂+1] = ∞
10 i = 1
11 j = 1
12 for k = p to r
13 if L[i] ≤ R[j]
14 A[k] = L[i]
15 i = i + 1
16 else A[k] = R[j]
17 j = j + 1

Analysis:

  • Time Complexity: Θ(n log n) in all cases
  • Space Complexity: Θ(n)
  • Recurrence: T(n) = 2T(n/2) + Θ(n)

Theorem 4.3: The recurrence T(n) = 2T(n/2) + cn has solution T(n) = Θ(n log n).

Proof: By Master Theorem. We have a = 2, b = 2, f(n) = cn. Since f(n) = Θ(n^log₂2) = Θ(n), we’re in case 2, so T(n) = Θ(n log n). □

4.4 Quick Sort

The Big Idea: Pick a “pivot” element, then partition the array so everything smaller goes left, everything larger goes right. Now recursively sort the two sides. It’s like organizing people by height around a chosen reference person.

Inspiration: Developed by Tony Hoare in 1960 while working on machine translation in Moscow. The genius lies in the partitioning step - one pass through the array puts the pivot in its final position and partially organizes everything else.

How it Works: Choose a pivot (often the last element), then use two pointers to partition the array. Elements smaller than pivot accumulate on the left, larger ones stay on the right. The pivot ends up in its correct final position, and we recursively sort the partitions.

Algorithm 4.5: QUICKSORT(A, p, r)

QUICKSORT(A, p, r)
1 if p < r
2 q = PARTITION(A, p, r)
3 QUICKSORT(A, p, q-1)
4 QUICKSORT(A, q+1, r)

Algorithm 4.6: PARTITION(A, p, r)

PARTITION(A, p, r)
1 x = A[r]
2 i = p - 1
3 for j = p to r - 1
4 if A[j] ≤ x
5 i = i + 1
6 exchange A[i] with A[j]
7 exchange A[i+1] with A[r]
8 return i + 1

Analysis:

  • Best Case: Θ(n log n) - balanced partitions
  • Worst Case: Θ(n²) - unbalanced partitions
  • Average Case: Θ(n log n)
  • Space Complexity: Θ(log n) to Θ(n) depending on partitioning

4.5 Heap Sort

The Big Idea: Build a “heap” - a binary tree where parents are always larger than children. Repeatedly extract the maximum (root) and rebuild the heap. It’s like having a self-organizing tournament bracket.

Inspiration: The heap data structure, introduced by J.W.J. Williams in 1964, combines the best of both worlds: we can find the maximum in O(1) time, and maintain the heap property in O(log n) time. It’s nature’s way of organizing priority.

How it Works: First, transform the array into a max-heap where A[i] ≥ A[2i] and A[i] ≥ A[2i+1]. Then repeatedly swap the root (maximum) with the last element, shrink the heap, and restore the heap property. The sorted elements accumulate at the end.

Algorithm 4.7: HEAPSORT(A)

HEAPSORT(A)
1 BUILD-MAX-HEAP(A)
2 for i = A.length downto 2
3 exchange A[1] with A[i]
4 A.heap-size = A.heap-size - 1
5 MAX-HEAPIFY(A, 1)

Algorithm 4.8: MAX-HEAPIFY(A, i)

MAX-HEAPIFY(A, i)
1 l = LEFT(i)
2 r = RIGHT(i)
3 if l ≤ A.heap-size and A[l] > A[i]
4 largest = l
5 else largest = i
6 if r ≤ A.heap-size and A[r] > A[largest]
7 largest = r
8 if largest ≠ i
9 exchange A[i] with A[largest]
10 MAX-HEAPIFY(A, largest)

Analysis:

  • Time Complexity: Θ(n log n) in all cases
  • Space Complexity: Θ(1)
  • In-place: Yes

Searching Algorithms

The Big Idea: The brute force approach - check every element one by one until you find what you’re looking for. It’s like looking for your keys by checking every pocket systematically.

Inspiration: This is the most natural search strategy humans use when items aren’t organized. Sometimes called “sequential search,” it’s the baseline against which all other search algorithms are measured.

How it Works: Start at the beginning and examine each element in sequence. If you find the target, return its position. If you reach the end without finding it, the element isn’t there. Simple, reliable, but potentially slow.

Algorithm 5.1: LINEAR-SEARCH(A, v)

LINEAR-SEARCH(A, v)
1 for i = 1 to A.length
2 if A[i] = v
3 return i
4 return NIL

Analysis:

  • Best Case: Θ(1) - element at first position
  • Worst Case: Θ(n) - element not present or at last position
  • Average Case: Θ(n/2) = Θ(n)

The Big Idea: Like playing “20 Questions” with a number. Always guess the middle, then eliminate half the possibilities based on “higher” or “lower.” It’s the optimal strategy for searching sorted data.

Inspiration: This divide-and-conquer approach dates back to ancient times but was first formalized for computers in the 1940s. The key insight: if data is sorted, you can eliminate half the search space with each comparison.

How it Works: Compare the target with the middle element. If they match, you’re done. If the target is smaller, search the left half. If larger, search the right half. Repeat until found or the search space is empty. Each step halves the problem size.

Precondition: Array A must be sorted.

Algorithm 5.2: BINARY-SEARCH(A, v)

BINARY-SEARCH(A, v)
1 left = 1
2 right = A.length
3 while left ≤ right
4 mid = ⌊(left + right)/2⌋
5 if A[mid] = v
6 return mid
7 else if A[mid] < v
8 left = mid + 1
9 else right = mid - 1
10 return NIL

Analysis:

  • Time Complexity: Θ(log n) in all cases
  • Space Complexity: Θ(1)
  • Recurrence: T(n) = T(n/2) + Θ(1) = Θ(log n)

Theorem 5.1: BINARY-SEARCH correctly finds element v in sorted array A.

Proof: By loop invariant. If v is in A, then v is in A[left..right] at the start of each iteration. This is maintained by the algorithm’s logic.

Algorithm 5.3: RECURSIVE-BINARY-SEARCH(A, v, left, right)

RECURSIVE-BINARY-SEARCH(A, v, left, right)
1 if left > right
2 return NIL
3 mid = ⌊(left + right)/2⌋
4 if A[mid] = v
5 return mid
6 else if A[mid] < v
7 return RECURSIVE-BINARY-SEARCH(A, v, mid+1, right)
8 else return RECURSIVE-BINARY-SEARCH(A, v, left, mid-1)

Analysis:

  • Time Complexity: Θ(log n)
  • Space Complexity: Θ(log n) due to recursion stack

Graph Algorithms

6.1 Graph Representation

Definition 6.1: A graph G = (V, E) consists of a finite set V of vertices and a finite set E of edges.

Adjacency Matrix: A |V| × |V| matrix A where A[i,j] = 1 if (i,j) ∈ E, 0 otherwise.

Adjacency List: For each vertex u ∈ V, maintain a list Adj[u] of all vertices v such that (u,v) ∈ E.

Algorithm 6.1: BFS(G, s)

BFS(G, s)
1 for each vertex u ∈ G.V - {s}
2 u.color = WHITE
3 u.d = ∞
4 u.π = NIL
5 s.color = GRAY
6 s.d = 0
7 s.π = NIL
8 Q = ∅
9 ENQUEUE(Q, s)
10 while Q ≠ ∅
11 u = DEQUEUE(Q)
12 for each v ∈ G.Adj[u]
13 if v.color = WHITE
14 v.color = GRAY
15 v.d = u.d + 1
16 v.π = u
17 ENQUEUE(Q, v)
18 u.color = BLACK

Analysis:

  • Time Complexity: O(V + E)
  • Space Complexity: O(V)

Theorem 6.1: BFS correctly computes shortest paths in unweighted graphs.

Algorithm 6.2: DFS(G)

DFS(G)
1 for each vertex u ∈ G.V
2 u.color = WHITE
3 u.π = NIL
4 time = 0
5 for each vertex u ∈ G.V
6 if u.color = WHITE
7 DFS-VISIT(G, u)

Algorithm 6.3: DFS-VISIT(G, u)

DFS-VISIT(G, u)
1 time = time + 1
2 u.d = time
3 u.color = GRAY
4 for each v ∈ G.Adj[u]
5 if v.color = WHITE
6 v.π = u
7 DFS-VISIT(G, v)
8 u.color = BLACK
9 time = time + 1
10 u.f = time

Analysis:

  • Time Complexity: Θ(V + E)
  • Space Complexity: O(V)

6.4 Dijkstra’s Algorithm

Algorithm 6.4: DIJKSTRA(G, w, s)

DIJKSTRA(G, w, s)
1 INITIALIZE-SINGLE-SOURCE(G, s)
2 S = ∅
3 Q = G.V
4 while Q ≠ ∅
5 u = EXTRACT-MIN(Q)
6 S = S ∪ {u}
7 for each vertex v ∈ G.Adj[u]
8 RELAX(u, v, w)

Algorithm 6.5: RELAX(u, v, w)

RELAX(u, v, w)
1 if v.d > u.d + w(u, v)
2 v.d = u.d + w(u, v)
3 v.π = u

Analysis:

  • Time Complexity: O((V + E) log V) with binary heap
  • Space Complexity: O(V)

Theorem 6.2: Dijkstra’s algorithm correctly computes shortest paths from source s to all vertices in a graph with non-negative edge weights.


Dynamic Programming

7.1 Principles of Dynamic Programming

Definition 7.1: Dynamic programming is an algorithmic technique for solving problems by breaking them down into simpler subproblems and storing the results of subproblems to avoid computing the same results again.

Key Properties:

  1. Optimal Substructure: Optimal solutions contain optimal solutions to subproblems
  2. Overlapping Subproblems: Recursive solution contains small number of distinct subproblems repeated many times

7.2 Fibonacci Numbers

Naive Recursive Approach:

FIBONACCI(n)
1 if n ≤ 1
2 return n
3 else return FIBONACCI(n-1) + FIBONACCI(n-2)

Analysis: T(n) = T(n-1) + T(n-2) + Θ(1) = Θ(φⁿ) where φ = (1+√5)/2

Dynamic Programming Approach:

FIBONACCI-DP(n)
1 if n ≤ 1
2 return n
3 let fib[0..n] be a new array
4 fib[0] = 0
5 fib[1] = 1
6 for i = 2 to n
7 fib[i] = fib[i-1] + fib[i-2]
8 return fib[n]

Analysis: Θ(n) time, Θ(n) space

7.3 Longest Common Subsequence

Problem: Given sequences X = ⟨x₁, x₂, …, xₘ⟩ and Y = ⟨y₁, y₂, …, yₙ⟩, find the length of their longest common subsequence.

Algorithm 7.1: LCS-LENGTH(X, Y)

LCS-LENGTH(X, Y)
1 m = X.length
2 n = Y.length
3 let c[0..m, 0..n] be a new table
4 for i = 1 to m
5 c[i, 0] = 0
6 for j = 0 to n
7 c[0, j] = 0
8 for i = 1 to m
9 for j = 1 to n
10 if X[i] = Y[j]
11 c[i, j] = c[i-1, j-1] + 1
12 else if c[i-1, j] ≥ c[i, j-1]
13 c[i, j] = c[i-1, j]
14 else c[i, j] = c[i, j-1]
15 return c[m, n]

Analysis: Θ(mn) time, Θ(mn) space

Recurrence Relation:

LCS[i,j] = {
0 if i = 0 or j = 0
LCS[i-1,j-1] + 1 if X[i] = Y[j]
max(LCS[i-1,j], LCS[i,j-1]) otherwise
}

7.4 0-1 Knapsack Problem

Problem: Given n items with weights w₁, w₂, …, wₙ and values v₁, v₂, …, vₙ, and a knapsack capacity W, maximize value while staying within weight limit.

Algorithm 7.2: KNAPSACK(w, v, W)

KNAPSACK(w, v, W)
1 n = w.length
2 let K[0..n, 0..W] be a new table
3 for i = 0 to n
4 K[i, 0] = 0
5 for w = 0 to W
6 K[0, w] = 0
7 for i = 1 to n
8 for w = 1 to W
9 if w[i-1] ≤ w
10 K[i, w] = max(v[i-1] + K[i-1, w-w[i-1]], K[i-1, w])
11 else K[i, w] = K[i-1, w]
12 return K[n, W]

Analysis: Θ(nW) time, Θ(nW) space


Advanced Topics

8.1 Divide and Conquer

Master Theorem: Let T(n) = aT(n/b) + f(n) where a ≥ 1, b > 1, and f(n) is asymptotically positive.

  1. If f(n) = O(n^(log_b a - ε)) for some ε > 0, then T(n) = Θ(n^log_b a)
  2. If f(n) = Θ(n^log_b a), then T(n) = Θ(n^log_b a log n)
  3. If f(n) = Ω(n^(log_b a + ε)) for some ε > 0, and af(n/b) ≤ cf(n) for some c < 1, then T(n) = Θ(f(n))

8.2 Greedy Algorithms

Definition 8.1: A greedy algorithm makes locally optimal choices at each step, hoping to find a global optimum.

Activity Selection Problem:

ACTIVITY-SELECTOR(s, f)
1 n = s.length
2 A = {a₁}
3 k = 1
4 for m = 2 to n
5 if s[m] ≥ f[k]
6 A = A ∪ {aₘ}
7 k = m
8 return A

8.3 Network Flow

Ford-Fulkerson Algorithm:

FORD-FULKERSON(G, s, t)
1 for each edge (u, v) ∈ G.E
2 (u, v).f = 0
3 while there exists a path p from s to t in the residual network Gf
4 cf(p) = min{cf(u, v) : (u, v) is in p}
5 for each edge (u, v) in p
6 if (u, v) ∈ E
7 (u, v).f = (u, v).f + cf(p)
8 else (v, u).f = (v, u).f - cf(p)

Analysis: O(E|f*|) where f* is maximum flow


References

  1. Cormen, T. H., Leiserson, C. E., Rivest, R. L., & Stein, C. (2009). Introduction to Algorithms (3rd ed.). MIT Press.

  2. Knuth, D. E. (1997). The Art of Computer Programming, Volume 1: Fundamental Algorithms (3rd ed.). Addison-Wesley.

  3. Knuth, D. E. (1998). The Art of Computer Programming, Volume 3: Sorting and Searching (2nd ed.). Addison-Wesley.

  4. Sedgewick, R., & Wayne, K. (2011). Algorithms (4th ed.). Addison-Wesley.

  5. Skiena, S. S. (2008). The Algorithm Design Manual (2nd ed.). Springer.

  6. Kleinberg, J., & Tardos, E. (2005). Algorithm Design. Addison-Wesley.

  7. Dasgupta, S., Papadimitriou, C. H., & Vazirani, U. V. (2006). Algorithms. McGraw-Hill.

  8. Levitin, A. (2011). Introduction to the Design and Analysis of Algorithms (3rd ed.). Addison-Wesley.


Exercises

Chapter 4: Sorting

4.1 Prove that any comparison-based sorting algorithm requires Ω(n log n) comparisons in the worst case.

4.2 Implement a hybrid sorting algorithm that uses insertion sort for small subarrays and merge sort for larger ones.

4.3 Analyze the number of inversions removed by one pass of bubble sort.

Chapter 5: Searching

5.1 Modify binary search to find the first occurrence of a repeated element.

5.2 Implement exponential search for unbounded arrays.

5.3 Prove the correctness of interpolation search for uniformly distributed data.

Chapter 6: Graph Algorithms

6.1 Implement topological sort using DFS.

6.2 Prove that Dijkstra’s algorithm works correctly with non-negative edge weights.

6.3 Implement the Bellman-Ford algorithm for graphs with negative edge weights.

Chapter 7: Dynamic Programming

7.1 Solve the coin change problem using dynamic programming.

7.2 Implement the Floyd-Warshall algorithm for all-pairs shortest paths.

7.3 Solve the matrix chain multiplication problem.


This textbook provides a rigorous mathematical foundation for understanding algorithms, suitable for gifted students transitioning from high school to advanced computer science studies. Each algorithm is presented with formal analysis, correctness proofs, and comprehensive examples.