C Programming Language Free Course Part-3
Arrays
Introduction to Arrays
An array is a collection of elements of the same data type stored in contiguous memory locations. Arrays allow you to store and manipulate large sets of data efficiently using a single variable name.
- Declaration:
To declare an array, you specify the data type, array name, and the number of elements.Example:
int numbers[10]; // An array of 10 integers
- Initialization:
Arrays can be initialized at the time of declaration.Example:
int numbers[5] = {1, 2, 3, 4, 5};
- Accessing Elements:
Elements of an array can be accessed using indices, starting from 0.Example:
int firstNumber = numbers[0]; // Accessing the first element
Operations on Arrays
- Traversing:
Accessing each element of the array sequentially.Example:
for (int i = 0; i < 5; i++) {
printf("%d ", numbers[i]);
}
- Insertion:
Adding elements at a specific position (usually involves shifting elements). - Deletion:
Removing elements from a specific position (also involves shifting). - Updating:
Modifying the value of elements at a specific index.
Sorting
Sorting is the process of arranging elements in a particular order. Here are three common sorting algorithms:
- Selection Sort:
Repeatedly finding the minimum element from the unsorted part and putting it at the beginning.Example:
void selectionSort(int arr[], int n) {
for (int i = 0; i < n - 1; i++) {
int minIndex = i;
for (int j = i + 1; j < n; j++) {
if (arr[j] < arr[minIndex]) {
minIndex = j;
}
}
// Swap the found minimum element with the first element
int temp = arr[minIndex];
arr[minIndex] = arr[i];
arr[i] = temp;
}
}
- Bubble Sort:
Repeatedly swapping adjacent elements if they are in the wrong order.cvoid bubbleSort(int arr[], int n) {
for (int i = 0; i < n - 1; i++) {
for (int j = 0; j < n - i - 1; j++) {
if (arr[j] > arr[j + 1]) {
// Swap arr[j] and arr[j+1]
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}}
- Insertion Sort:
Building a sorted array one element at a time by repeatedly inserting elements into their correct position.Example:
void insertionSort(int arr[], int n) {
for (int i = 1; i < n; i++) {
int key = arr[i];
int j = i - 1;
while (j >= 0 && arr[j] > key) {
arr[j + 1] = arr[j];
j--;
}
arr[j + 1] = key;
}
}
Searching
Searching is the process of finding the location of a given element within an array.
- Linear Search:
Checks each element of the array one by one until the desired element is found or the array ends.Example:
int linearSearch(int arr[], int n, int x) {
for (int i = 0; i < n; i++) {
if (arr[i] == x){
return i; // Return the index of the element
}
}
return -1; // Element not found
}
- Binary Search:
Requires the array to be sorted. It divides the array into halves to find the element efficiently.Example:
int binarySearch(int arr[], int n, int x) {
int left = 0, right = n - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (arr[mid] == x) {
return mid; // Element found
} else if (arr[mid] < x) {
left = mid + 1;
} else {
right = mid - 1;
}}return -1; // Element not found}
Multidimensional Arrays
- Definition:
Multidimensional arrays are arrays of arrays. The most common is a two-dimensional array, which can be thought of as a matrix or a table. - Declaration:
int matrix[3][3]; // A 3x3 matrix
- Initialization:
int matrix[2][2] = {{1, 2}, {3, 4}};
- Accessing Elements:
int element = matrix[0][1]; // Accessing the element in the first row, second column
Pointers and Arrays
Pointers and arrays have a close relationship in C, as the name of an array is a pointer to its first element.
- Pointer to Array:
Example:
int arr[5] = {1, 2, 3, 4, 5};
int *ptr = arr; // Pointer to the first element of the array
- Accessing Array Elements Using Pointers:
Example:
for (int i = 0; i < 5; i++) {
printf("%d ", *(ptr + i)); // Accessing elements using pointer arithmetic
}
Pointer and 2-D Arrays
- Pointer to 2-D Array:
A 2-D array can be accessed using pointers by first pointing to the array’s rowExample:
.
int matrix[3][3];int (*ptr)[3] = matrix; // Pointer to an array of 3 integers
- Accessing Elements Using Pointers:
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
printf("%d ", *(*(ptr + i) + j));
}
printf("\n");
}
Array of Pointers
An array of pointers can store addresses of different data types or strings.
Example:
char *names[] = {"Alice", "Bob", "Charlie"};
printf("%s", names[0]); // Accessing the first string
Dynamic Memory Allocation
Dynamic memory allocation allows you to allocate memory during runtime using functions from <stdlib.h>.
- Functions:
malloc(): Allocates memory but does not initialize it.calloc(): Allocates and initializes memory to zero.realloc(): Resizes previously allocated memory.free(): Frees allocated memory.
Example:
int *arr;
arr = (int *)malloc(5 * sizeof(int)); // Allocate memory for 5 integers
if (arr != NULL) {
// Use the allocated memory
for (int i = 0; i < 5; i++) {
arr[i] = i;
}
// Free the allocated memory
free(arr);
}
Structures
Structure Declaration
A structure is a user-defined data type that allows you to group different types of variables under one name.
Example:
struct Person {
char name[50];
int age;
float height;
};
Operations on Structures
- Creating Structure Variables:
struct Person person1;
- Accessing Members:
person1.age = 30;
strcpy(person1.name, "John");
- Initialization:
struct Person person2 = {"Alice", 25, 5.5};
Nesting of Structures
You can nest one structure within another to create complex data models.
struct Address {
char city[50];
int zip;
};struct Employee {
char name[50];
struct Address address; // Nested structure
};
Array of Structures
An array of structures allows you to store multiple records of the same type.
struct Person people[3];
people[0].age = 20;
Difference Between Arrays and Structures
- Arrays:
- Store elements of the same data type.
- Elements are accessed using indices.
- Fixed size once declared.
- Structures:
- Store elements of different data types.
- Members are accessed using the dot (
.) operator. - Size depends on the combined size of all members.
Passing Structures to Functions
Structures can be passed to functions by value or by reference (using pointers).
- By Value:
void printPerson(struct Person p) {printf