🔴 Advanced · Lesson 46

Dynamic Structures

Dynamic structures are structure variables created at run time using dynamic memory allocation. They are useful when the number of records is decided during execution.

Single struct allocation

C Language

#include <stdio.h>
#include <stdlib.h>

struct Student {
    int roll;
    char name[30];
    float marks;
};

int main() {
    struct Student *s = (struct Student*) malloc(sizeof(struct Student));
    if(s == NULL) return 1;

    s->roll = 101;
    sprintf(s->name, "Aman");
    s->marks = 88.5;

    printf("%d %s %.1f", s->roll, s->name, s->marks);
    free(s);
    return 0;
}

Array of structures dynamically

C Language

struct Student *students;
int n;
scanf("%d", &n);
students = malloc(n * sizeof(struct Student));

for(int i = 0; i < n; i++) {
    scanf("%d %s %f", &students[i].roll, students[i].name, &students[i].marks);
}

free(students);

Arrow Operator

Expression	Meaning
`s.roll`	Use when s is a structure variable
`s->roll`	Use when s is a pointer to structure
`(*s).roll`	Same as s->roll

Summary

Dynamic structure is allocated using malloc
Use -> operator with structure pointer
Array of structures can be allocated dynamically
Always check allocation failure
Always free allocated memory

Dynamic Structures

Dynamic structures run time पर memory allocate करके बनाए जाते हैं। जब records की संख्या पहले से fixed न हो, तब ये useful होते हैं।

Single struct allocation

C Language

struct Student *s = malloc(sizeof(struct Student));
s->roll = 101;
s->marks = 88.5;
free(s);

Array of structures

C Language

struct Student *students;
students = malloc(n * sizeof(struct Student));
free(students);

Arrow Operator

Expression	Meaning
`s.roll`	Structure variable के साथ
`s->roll`	Structure pointer के साथ
`(*s).roll`	s->roll जैसा ही

सारांश

Dynamic structure malloc से allocate होती है
Structure pointer के साथ -> use करें
Records run time पर create कर सकते हैं
Allocation fail check करें
free करना जरूरी है

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