1.Create a student database using an array of structures and apply sorting techniques (Bubble Sort, Insertion Sort, Selection Sort).
#include <stdio.h>
#include <string.h>

struct Student {
    int rollno;
    char name[50];
    float marks;
};

void display(struct Student s[], int n) {
    printf("\nRollNo\tName\tMarks\n");
    for (int i = 0; i < n; i++) {
        printf("%d\t%s\t%.2f\n", s[i].rollno, s[i].name, s[i].marks);
    }
}

// Bubble Sort
void bubbleSort(struct Student s[], int n) {
    struct Student temp;
    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (s[j].marks > s[j + 1].marks) {
                temp = s[j];
                s[j] = s[j + 1];
                s[j + 1] = temp;
            }
        }
    }
}

// Insertion Sort
void insertionSort(struct Student s[], int n) {
    int i, j;
    struct Student key;
    for (i = 1; i < n; i++) {
        key = s[i];
        j = i - 1;
        while (j >= 0 && s[j].marks > key.marks) {
            s[j + 1] = s[j];
            j--;
        }
        s[j + 1] = key;
    }
}

// Selection Sort
void selectionSort(struct Student s[], int n) {
    int i, j, min;
    struct Student temp;
    for (i = 0; i < n - 1; i++) {
        min = i;
        for (j = i + 1; j < n; j++) {
            if (s[j].marks < s[min].marks)
                min = j;
        }
        temp = s[i];
        s[i] = s[min];
        s[min] = temp;
    }
}

int main() {
    struct Student s[50];
    int n, choice;

    printf("Enter number of students: ");
    scanf("%d", &n);

    for (int i = 0; i < n; i++) {
        printf("\nEnter details of student %d\n", i + 1);
        printf("Roll No: ");
        scanf("%d", &s[i].rollno);
        printf("Name: ");
        scanf("%s", s[i].name);
        printf("Marks: ");
        scanf("%f", &s[i].marks);
    }

    printf("\nChoose Sorting Technique:\n");
    printf("1. Bubble Sort\n2. Insertion Sort\n3. Selection Sort\nEnter choice: ");
    scanf("%d", &choice);

    switch (choice) {
        case 1:
            bubbleSort(s, n);
            printf("\nAfter Bubble Sort (by Marks):");
            display(s, n);
            break;
        case 2:
            insertionSort(s, n);
            printf("\nAfter Insertion Sort (by Marks):");
            display(s, n);
            break;
        case 3:
            selectionSort(s, n);
            printf("\nAfter Selection Sort (by Marks):");
            display(s, n);
            break;
        default:
            printf("\nInvalid choice!");
    }

    return 0;
}