DSA 3 DAYS Part 2

1. Introduction to Arrays

An array is a data structure used to store a collection of elements, typically of the same data type, in contiguous memory locations. Arrays allow efficient indexing and manipulation of data, making them a fundamental building block in programming and computer science.

---

2. Definition

An array is a data structure that stores a fixed-size, ordered collection of elements of the same data type in contiguous memory locations. This arrangement allows efficient access and manipulation using indices.

---

3. One-Dimensional Array and Multi-Dimensional Array

a. One-Dimensional Array
A one-dimensional array is a linear data structure that stores elements of the same data type in a sequential manner. These elements are accessed using a single index. It is often referred to as a list.
Example:

int arr[5] = {1, 2, 3, 4, 5};

b. Multi-Dimensional Array
A multi-dimensional array is a data structure that stores data in a tabular or grid-like format across two or more dimensions. Each element is accessed using multiple indices.
Example (Two-dimensional array):

int matrix[3][3];

---

4. Pointer

A pointer is a variable that stores the memory address of another variable. It is a core feature in programming, particularly in languages like C and C++, which allows direct access and manipulation of memory locations.

Syntax:

int a = 10;  
int *ptr = &a;  
printf("%p", ptr);

---

5. Pointer to Structure

In C, a pointer to a structure is used to store the address of a structure variable. This allows indirect access to the structure’s members, and is especially useful for dynamic memory allocation and passing structures to functions efficiently.

Example Code:

#include <stdio.h>

struct Person {
    char name[50];
    int age;
};

int main() {
    struct Person p1 = {"Alice", 30};
    struct Person *ptr = &p1;

    printf("Name: %s\n", ptr->name);
    printf("Age: %d\n", ptr->age);

    return 0;
}

---

6. Various Programs for Array Operations

i. Insertion

a. Insert at Beginning

insert_first(Array, n, max, data)
Step 1: Start
Step 2: If n = max, show Overflow and exit
Step 3: Repeat Step 4 for i = n down to 0
Step 4: arr[i + 1] = arr[i]
Step 5: arr[0] = data
Step 6: n = n + 1
Step 7: End

b. Insert at Last

insert_last(Array, n, max, data)
Step 1: Start
Step 2: If n = max, show Overflow and exit
Step 3: arr[n] = data
Step 4: n = n + 1
Step 5: End

c. Insert at Specific Position

insert_specific(Array, n, max, data, k)
Step 1: Start
Step 2: If n = max, show Overflow and exit
Step 3: Repeat Step 4 for i = n down to k
Step 4: arr[i + 1] = arr[i]
Step 5: arr[k] = data
Step 6: n = n + 1
Step 7: End

ii. Deletion

a. Deletion at Beginning

delete_first(Array, n)
Step 1: Start
Step 2: If n = 0, show Underflow and exit
Step 3: Repeat Step 4 for i = 0 to n - 1
Step 4: arr[i] = arr[i + 1]
Step 5: n = n - 1
Step 6: End

b. Deletion at Last

delete_last(Array, n)
Step 1: Start
Step 2: If n = 0, show Underflow and exit
Step 3: n = n - 1
Step 4: End

c. Deletion at Specific Position

delete_specific(Array, n, k)
Step 1: Start
Step 2: If n = 0, show Underflow and exit
Step 3: Repeat Step 4 for i = k to n - 1
Step 4: arr[i] = arr[i + 1]
Step 5: n = n - 1
Step 6: End

---

7. Introduction to Strings

A string is a sequence of characters used to represent text in programming. In C, strings are implemented as arrays of characters, terminated by a special null character '\0', which indicates the end of the string.

String Library Functions

1. strcat()
   Concatenates (appends) the source string (src) to the destination string (dest).
   Syntax:

char *strcat(char *dest, const char *src);

2. strncat()
   Concatenates at most n characters from the source string (src) to the destination string (dest).
   Syntax:

char *strncat(char *dest, const char *src, size_t n);

3. strlen()
   Returns the length of a string (excluding the null terminator).
   Syntax:

size_t strlen(const char *str);

4. strcpy()
   Copies the source string (src) to the destination string (dest).
   Syntax:

char *strcpy(char *dest, const char *src);

5. strncpy()
   Copies at most n characters from the source string (src) to the destination string (dest). If src is shorter than n, the rest of dest is filled with null characters.
   Syntax:

char *strncpy(char *dest, const char *src, size_t n);

6. strcmp()
   Compares two strings lexicographically.

• Returns 0 if strings are equal.
• Returns a negative value if the first string is less than the second.
• Returns a positive value if the first string is greater than the second.
  Syntax:

int strcmp(const char *str1, const char *str2);

7. strncmp()
   Compares at most n characters of two strings lexicographically.
   Syntax:

int strncmp(const char *str1, const char *str2, size_t n);

---