Example: Find Roots of Quadratic Equation using Switch Statement in C

// Find Roots of Quadratic Equation using Switch Statement
#include <stdio.h>
#include <math.h> // Required for sqrt() function

int main() {
    // Step 1: Declare variables for coefficients and roots
    double a, b, c;
    double discriminant, root1, root2, realPart, imagPart;
    int choice; // To control the switch statement

    // Step 2: Prompt user for coefficients
    printf("Enter coefficients a, b and c: ");
    scanf("%lf %lf %lf", &a, &b, &c);

    // Step 3: Handle the case where 'a' is zero (not a quadratic equation)
    if (a == 0) {
        if (b == 0) {
            if (c == 0) {
                printf("Infinite solutions (0=0).\n");
            } else {
                printf("No solution (c=0, where c!=0).\n");
            }
        } else {
            // Linear equation: bx + c = 0 => x = -c/b
            root1 = -c / b;
            printf("This is a linear equation.\n");
            printf("Root = %.2lf\n", root1);
        }
        return 0; // Exit if not a quadratic equation
    }

    // Step 4: Calculate the discriminant
    discriminant = b * b - 4 * a * c;

    // Step 5: Determine the 'choice' value for the switch statement
    if (discriminant > 0) {
        choice = 1; // Distinct real roots
    } else if (discriminant == 0) {
        choice = 0; // Equal real roots
    } else {
        choice = -1; // Complex roots
    }

    // Step 6: Use switch statement to find roots based on 'choice'
    switch (choice) {
        case 1: // Discriminant > 0 (Distinct Real Roots)
            root1 = (-b + sqrt(discriminant)) / (2 * a);
            root2 = (-b - sqrt(discriminant)) / (2 * a);
            printf("Roots are real and distinct.\n");
            printf("Root1 = %.2lf\n", root1);
            printf("Root2 = %.2lf\n", root2);
            break;

        case 0: // Discriminant = 0 (Equal Real Roots)
            root1 = root2 = -b / (2 * a);
            printf("Roots are real and equal.\n");
            printf("Root1 = Root2 = %.2lf\n", root1);
            break;

        case -1: // Discriminant < 0 (Complex Roots)
            realPart = -b / (2 * a);
            imagPart = sqrt(-discriminant) / (2 * a);
            printf("Roots are complex and distinct.\n");
            printf("Root1 = %.2lf + %.2lfi\n", realPart, imagPart);
            printf("Root2 = %.2lf - %.2lfi\n", realPart, imagPart);
            break;
    }

    return 0;
}