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# Lecture 12: RECAP Review of Lectures 1-11 Foundations
## Lecture 1: Introduction to Programming ### Key Topics - Programming concepts: algorithms, syntax, logic, debugging - Computer fundamentals: binary system, CPU, memory, storage - High-level vs low-level languages - Hello World program structure - C++ development setup - Problem-solving methodology - Comments and variables: data types, static typing
## Lecture 1: Code Example ```cpp #include <iostream> using namespace std; int main() { cout << "Hello, World!" << endl; // Output text return 0; // Indicate success } ```
** Error Example:** ```cpp #include <iostream> using namespace std; int main() { cout << "Hello, World!" << endl return 0; } ``` --- **Error Message:** `expected ';' before 'return'` **Error Type:** Syntax Error (compile-time) **Resolution:** Add the missing semicolon at the end of the statement. ```cpp cout << "Hello, World!" << endl; ```
## Lecture 2: C++ Data Types ### Key Topics - Data types: memory size, permissible operations - Primitive types: integers, floating-point, characters, booleans - Type modifiers: signed/unsigned, short/long - std::string for text handling - Type inference with auto - const qualifier for read-only variables - Type casting with static_cast - Variables as named memory storage
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## Lecture 2: Code Example ```cpp #include <iostream> #include <string> using namespace std; int main() { int score = 100; // Integer double price = 19.99; // Floating-point char grade = 'A'; // Character bool pass = true; // Boolean string name = "Student"; // String const int maxScore = 100; // Const cout << "Score: " << score << endl; return 0; } ```
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**Error Example:** ```cpp #include <iostream> #include <string> using namespace std; int main() { int score = "A"; cout << "Score: " << score << endl; return 0; } ``` --- **Error Message:** `error: cannot convert 'const char [2]' to 'int' in initialization` **Error Type:** Type Mismatch / Compile-time error **Resolution:** Use a compatible type. If the value is a character use `char`, or use a string for text. ```cpp char score = 'A'; // or string scoreStr = "A"; ```
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## Lecture 3: C++ Fundamentals ### Key Topics - Basic program structure: #include, namespaces, int main(), return 0 - Operators: arithmetic, assignment, comparison, logical, increment, scope resolution - Operator precedence and parentheses - Variable scope: local vs global, lifetime - Storage classes: static, extern
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## Lecture 3: Code Example ```cpp #include <iostream> using namespace std; // Global variable int globalVar = 10; int main() { int a = 5, b = 3; // Local variables int sum = a + b; // Arithmetic operators bool condition = (a > b); // Comparison cout << "Sum: " << sum << endl; return 0; } ```
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**Error Example:** ```cpp #include <iostream> using namespace std; int main() { int a = 5; cout << "Sum: " << a + b << endl; return 0; } ``` --- **Error Message:** `error: 'b' was not declared in this scope` **Error Type:** Name Resolution / Compile-time error **Resolution:** Declare the variable before using it. ```cpp int a = 5; int b = 10; // Declare first cout << "Sum: " << a + b << endl; // Now ok ```
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## Lecture 4: Conditionals ### Key Topics - Why conditionals: decision-making in programs - C++ conditional tools: if, else if, else, switch - Boolean expressions: true/false evaluation
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## Lecture 4: Code Example ```cpp #include <iostream> using namespace std; int main() { int score = 85; if (score >= 90) { cout << "Grade: A" << endl; } else if (score >= 80) { cout << "Grade: B" << endl; } else { cout << "Grade: C" << endl; } return 0; } ```
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**Error Example:** ```cpp #include <iostream> using namespace std; int main() { int x = 5; if (x = 10) { cout << "x is 10" << endl; } return 0; } ``` --- **Error Message:** None (runs but logic is wrong), always evaluates to true. **Error Type:** Logic Error (assignment used instead of comparison) **Resolution:** Use `==` for comparison. ```cpp if (x == 10) { // Fixed cout << "x is 10" << endl; } ```
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## Lecture 5: Loops ### Key Topics - Why loops: automating repetitive tasks - while loop: condition checked before execution - for loop: counting iterations with initialization, condition, increment - do-while loop: body executed at least once, condition after
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## Lecture 5: Code Example ```cpp #include <iostream> using namespace std; int main() { for (int i = 1; i <= 5; ++i) { cout << "Count: " << i << endl; } int j = 1; while (j <= 3) { cout << "While loop: " << j << endl; ++j; } return 0; } ```
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**Error Example:** ```cpp #include <iostream> using namespace std; int main() { while (true) { cout << "This will loop forever!" << endl; } return 0; } ``` --- **Error Message:** Program runs indefinitely (infinite loop). **Error Type:** Logic Error / Runtime (infinite loop) **Resolution:** Ensure the condition eventually becomes false. ```cpp int x = 0; while (x < 5) { // Fixed - condition becomes false cout << x << endl; x++; } ```
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## Lecture 6: Arrays ### Key Topics - Why arrays: store lists of data - Declaration and initialization: fixed size, automatic sizing - Accessing elements: zero-based indexing - Out-of-bounds access danger - std::vector alternative: dynamic sizing, safety
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## Lecture 6: Code Example ```cpp #include <iostream> #include <vector> using namespace std; int main() { int arr[5] = {10, 20, 30, 40, 50}; cout << "First element: " << arr[0] << endl; vector<int> vec = {1, 2, 3}; vec.push_back(4); cout << "Vector size: " << vec.size() << endl; return 0; } ```
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**Error Example:** ```cpp #include <iostream> using namespace std; int main() { int arr[5] = {1, 2, 3, 4, 5}; cout << arr[5] << endl; return 0; } ``` --- **Error Message:** Undefined behavior (garbage value or crash). **Error Type:** Runtime / Undefined Behavior (out-of-bounds access) **Resolution:** Check array bounds or use safer containers like `std::vector` and `at()`. ```cpp if (5 < 5) { // Valid index check cout << arr[5] << endl; } ```
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## Lecture 7: Functions ### Key Topics - Why functions: modularity, reuse, abstraction - Declaration vs definition - Parameters & returns: passing by value, reference, const reference - Function overloading
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## Lecture 7: Code Example ```cpp #include <iostream> using namespace std; // Function declaration int add(int a, int b); int main() { int result = add(5, 3); cout << "5 + 3 = " << result << endl; return 0; } // Function definition int add(int a, int b) { return a + b; } ```
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**Error Example:** ```cpp #include <iostream> using namespace std; int main() { int result = add(5, 3); cout << result << endl; return 0; } int add(int a, int b) { return a + b; } ``` --- **Error Message:** `error: 'add' was not declared in this scope` **Error Type:** Linker/Declaration error (compile-time) **Resolution:** Provide a forward declaration or move the function definition before `main`. **Fixed:** ```cpp int add(int a, int b); // Declaration int main() { int result = add(5,3); cout << result << endl; return 0; } int add(int a, int b) { return a + b; } ```
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## Lecture 8: Structures & Pointers ### Key Topics - Structs for data grouping - Accessing members: dot (.) for objects, arrow (->) for pointers - Efficient passing: const reference for large structs - Memory layout & padding - Pointers basics: addresses, dereferencing - Self-referential structs, linked lists
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## Lecture 8: Code Example ```cpp #include <iostream> using namespace std; struct Person { string name; int age; }; int main() { Person p = {"Alice", 25}; cout << p.name << " is " << p.age << endl; Person* ptr = &p; ptr->age = 26; // Arrow operator cout << "New age: " << p.age << endl; return 0; } ```
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**Error Example:** ```cpp #include <iostream> using namespace std; struct Node { int data; Node* next; }; int main() { Node* node = nullptr; cout << node->data << endl; return 0; } ``` --- **Error Message:** Segmentation fault or program crash at runtime. **Error Type:** Runtime Error (null pointer dereference) **Resolution:** Validate pointers before dereferencing; allocate memory when needed. **Fixed:** ```cpp Node* node = new Node{10, nullptr}; if (node != nullptr) { cout << node->data << endl; } delete node; // cleanup ```
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## Lecture 9: Dynamic Memory & Linked Lists ### Key Topics - Dynamic memory allocation problem: fixed-size limitations - C style: malloc/free - C++ style: new/delete, new[]/delete[] - Memory leaks and dangling pointers - Exception handling in allocation - Smart pointers for automatic memory management - Linked lists implementation
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## Lecture 9: Code Example ```cpp #include <iostream> using namespace std; int main() { // Dynamic allocation int* arr = new int[5]; for(int i = 0; i < 5; ++i) arr[i] = i*10; cout << "Dynamic array: "; for(int i = 0; i < 5; ++i) cout << arr[i] << " "; cout << endl; // Deallocate delete[] arr; return 0; } ```
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**Error Example (Dangling pointer / Use-after-free):** ```cpp #include <iostream> using namespace std; int main() { int* ptr = new int(10); cout << *ptr << endl; // prints 10 delete ptr; cout << *ptr << endl; // undefined behavior - use after delete return 0; } ``` --- **Error Message:** Undefined behavior (may crash, print garbage, or appear to work). **Error Type:** Runtime Error (dangling pointer / use-after-free) **Resolution:** Do not access memory after `delete`. Set pointer to `nullptr` after deletion or avoid raw pointers; use smart pointers. **Fixed:** ```cpp int* ptr = new int(10); cout << *ptr << endl; delete ptr; ptr = nullptr; // avoid dangling pointer // guard before use: if (ptr) cout << *ptr << endl; ``` **Preferred modern fix (smart pointer):** ```cpp #include <memory> auto sp = std::make_unique<int>(10); cout << *sp << endl; // automatic cleanup ```
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## Lecture 10: Data Structures & Algorithms ### Key Topics - Data structures and algorithms introduction - Linear search and time complexity basics - Stack and Queue data structures - Bubble sort algorithm
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## Lecture 10: Code Example ```cpp #include <iostream> using namespace std; // Simple stack using array int stack[10]; int top = -1; void push(int val) { stack[++top] = val; } int pop() { return top >= 0 ? stack[top--] : -1; } int main() { push(10); push(20); cout << "Popped: " << pop() << endl; // Bubble sort int arr[] = {5, 3, 8, 1}; for(int i = 0; i < 3; ++i) { for(int j = 0; j < 3-i; ++j) { if(arr[j] > arr[j+1]) { swap(arr[j], arr[j+1]); } } } cout << "Sorted: "; for(int x : arr) cout << x << " "; return 0; } ```
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## Lecture 10: Common Error - Off-by-One Error **Error Example:** ```cpp #include <iostream> using namespace std; int main() { int arr[5] = {1, 2, 3, 4, 5}; for(int i = 0; i <= 5; ++i) { // <= 5 instead of < 5 cout << arr[i] << " "; } return 0; } ``` --- **Error Message:** Accesses arr[5] which is out of bounds — undefined behavior. **Error Type:** Logic Error / Runtime (off-by-one) **Resolution:** Use correct bounds (`i < size`) or iterate using container size. ```cpp for(int i = 0; i < 5; ++i) { // Fixed cout << arr[i] << " "; } ```
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## Lecture 11: Data Structures and Algorithms II ### Key Topics - Binary search in sorted arrays (O(log n)) - Binary Search Trees: insert, search operations - Heap data structure: max/min heaps, heap sort - Merge sort: divide and conquer, stable sorting (O(n log n))
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## Lecture 11: Code Example ```cpp #include <iostream> using namespace std; // Binary search int binarySearch(int arr[], int n, int target) { int left = 0, right = n-1; while(left <= right) { int mid = left + (right - left)/2; if(arr[mid] == target) return mid; arr[mid] < target ? left = mid+1 : right = mid-1; } return -1; } int main() { int sortedArr[] = {1, 3, 5, 7, 9}; int pos = binarySearch(sortedArr, 5, 7); cout << "Target found at index: " << pos << endl; return 0; } ```
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## Lecture 11: Common Error - Binary Search on Unsorted Array **Error Example:** ```cpp #include <iostream> using namespace std; int binarySearch(int arr[], int n, int target) { int left = 0, right = n-1; while(left <= right) { int mid = left + (right - left)/2; if(arr[mid] == target) return mid; arr[mid] < target ? left = mid+1 : right = mid-1; } return -1; } int main() { int unsortedArr[] = {5, 2, 8, 1, 9}; // Not sorted int pos = binarySearch(unsortedArr, 5, 8); cout << "Position: " << pos << endl; return 0; } ``` --- **Error Message:** Binary search returns -1 (not found) even when element exists. **Error Type:** Precondition Violation / Logic Error (algorithm used on invalid input) **Resolution:** Ensure preconditions are met: sort the array prior to binary search or use a linear search on unsorted data. **Fixed (sort first):** ```cpp #include <algorithm> int sortedArr[] = {1, 2, 5, 8, 9}; int pos = binarySearch(sortedArr, 5, 8); ```
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