Algorithm Design and Pseudocode

Algorithm Design

• Problem-solving approach:
  • Understand the problem
  • Break down into smaller sub-problems
  • Develop a step-by-step solution
  • Implement and test the solution
• Algorithm design techniques:
  • Divide and Conquer
  • Dynamic Programming
  • Greedy Algorithms
  • Backtracking

Pseudocode

• Definition: A high-level representation of a programming algorithm using structured English-like syntax
• Purpose: To design, test, and communicate algorithms without worrying about specific programming languages
• Features:
  • Simple syntax
  • Easy to read and write
  • Language-independent

Conditional Statements

• Definition: Statements that execute different blocks of code based on conditions or predicates
• Types:
  • If-Then statements
  • If-Then-Else statements
  • Switch statements (or Case statements)
• Logical Operators:
  • AND (&&)
  • OR (||)
  • NOT (!)

Control Structures

• Definition: Statements that control the flow of program execution
• Types:
  • Conditional Statements (If-Then, If-Then-Else, Switch)
  • Loops (For, While, Do-While)
  • Jump Statements (Break, Continue, Return)
• Purpose: To alter the normal flow of program execution based on conditions, iterations, or jumps

Iterations (Loops)

• Definition: Statements that execute a block of code repeatedly for a specified number of iterations
• Types:
  • For loops
  • While loops
  • Do-While loops
• Loop Control Variables:
  • Initialization
  • Condition
  • Increment/Decrement

Algorithm Design

• Algorithm design involves a problem-solving approach that includes understanding the problem, breaking it down into smaller sub-problems, developing a step-by-step solution, implementing, and testing the solution
• Techniques used in algorithm design include Divide and Conquer, Dynamic Programming, Greedy Algorithms, and Backtracking

Pseudocode

• Pseudocode is a high-level representation of a programming algorithm using structured English-like syntax
• Its purpose is to design, test, and communicate algorithms without worrying about specific programming languages
• Pseudocode features simple syntax, is easy to read and write, and is language-independent

Conditional Statements

• Conditional statements execute different blocks of code based on conditions or predicates
• Types of conditional statements include If-Then statements, If-Then-Else statements, and Switch statements (or Case statements)
• Logical operators used in conditional statements include AND (&&), OR (||), and NOT (!)

Control Structures

• Control structures alter the normal flow of program execution based on conditions, iterations, or jumps
• Types of control structures include Conditional Statements, Loops, and Jump Statements
• Conditional Statements include If-Then, If-Then-Else, and Switch statements
• Loops include For, While, and Do-While loops
• Jump Statements include Break, Continue, and Return statements

Iterations (Loops)

• Loops execute a block of code repeatedly for a specified number of iterations
• Types of loops include For loops, While loops, and Do-While loops
• Loop control variables involve Initialization, Condition, and Increment/Decrement

Problem Solving with Selection and Repetition Statements

• The objectives of this unit are:
  • Using relational and logical operators
  • Using selection statements to choose between two or more execution paths in a program
  • Using repetition statements to repeat a segment of code

Control Structures

• There are two types of control flow:
  • Sequential control flow: one statement after another
  • Non-sequential control flow: statements can be executed or skipped based on conditions

Selection Structures

• C provides two control structures that allow the selection of a group of statements to be executed or skipped when certain conditions are met:
  • if statement
  • if-else statement

Conditional Expressions

• A condition is an expression evaluated to true or false
• Conditions are composed of expressions combined with relational operators
• Examples of relational operators:
  • < (less than)
  • > (greater than)
  • >= (greater than or equal to)
  • == (equal to)
  • != (not equal to)

Logical Operators

• Complex conditions can be created by combining two or more boolean expressions using logical operators:
  • && (and)
  • || (or)
  • ! (not)

Evaluation of Boolean Expressions

• The evaluation of a boolean expression is done according to the precedence and associativity of the operators
• Always add parentheses for readability

Caution

• Be careful when writing boolean expressions, as the values 0 and 1 are used to represent false and true respectively
• Avoid convoluted codes and use parentheses for readability

Short-Circuit Evaluation

• Short-circuit evaluation is used to avoid evaluating unnecessary expressions
• || (or) operator: if the first expression is true, skip evaluating the second expression and return true
• && (and) operator: if the first expression is false, skip evaluating the second expression and return false

if and if-else Statements

• Examples of if and if-else statements
• Use parentheses for readability
• Move common statements out of the if-else construct

Nested if and if-else Statements

• Nested if (if-else) structures refer to the containment of an if (if-else) structure within another if (if-else) structure
• Use parentheses and indentation to improve readability

Style Issues

• Indentation is important for readability
• Use consistent indentation and formatting
• Alternative indentation style for deeply nested if-else-if construct
• Name 'boolean' variables descriptively to improve readability### Naming Conventions for Boolean Flags
• Add suffixes such as "is" or "has" to names of boolean flags instead of just calling them "flag"
• Example: isEven, isPrime, hasError, hasDuplicates

Removing 'if' Statements with Assignment

• The if statement can be rewritten into a single assignment statement when the condition evaluates to 0 or 1
• Example: isEven = (num % 2 == 0);

Common Errors

• Errors can be caught by the compiler or may go undetected
• Example: extra semicolon at the end of an if statement, incorrect indentation, mismatched else statement

The switch Statement

• Alternative to if-else-if statements
• Restriction: value must be of discrete type (e.g., int, char)
• Syntax: switch (expression) { case value1: ...; break; ... default: ...; break; }

Testing and Debugging

• Test your programs thoroughly with your own data
• Do not rely on CodeCrunch to test your programs
• Example: finding the maximum value among three variables

The while Loop

• Syntax: while (condition) { loop body }
• Loop body is executed as long as the condition is true
• Example: keep prompting the user to input a non-negative integer and print the maximum integer input

The do-while Loop

• Syntax: do { loop body } while (condition);
• Loop body is executed at least once
• Example: count the number of digits in an integer

The for Loop

• Syntax: for (initialization; condition; update) { loop body }
• Example: print numbers 1 to 10