superdemo.java

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int n, m = 0, i = 0, j = 0;
char a[10][10], f[10], visited[10];

void follow(char c);
void first(char c);

void main() {
    int i, z;
    char c, ch;

    printf("Enter the number of productions:\n");
    scanf("%d", &n);

    printf("Enter the productions (in the format: A->B):\n");
    // Read productionssca
    for(i = 0; i < n; i++) {
        scanf("%s%c", a[i], &ch); // Read each production rule
    }

    do {
        m = 0; // Reset the set for each query
        memset(f, 0, sizeof(f)); // Clear the array to avoid garbage values
        printf("Enter the element whose FIRST & FOLLOW is to be found: ");
        scanf(" %c", &c); // Notice the space before %c to consume newline character

        // Calculate and display FIRST
        first(c);
        printf("FIRST(%c) = {", c);
        for(i = 0; i < m; i++) {
            printf("%c", f[i]);
            if (i != m - 1) printf(", ");
        }
        printf("}\n");

        // Reset for FOLLOW calculation
        m = 0; 
        memset(f, 0, sizeof(f)); // Reset the set for FOLLOW calculation
        
        // Calculate and display FOLLOW
        follow(c);
        printf("FOLLOW(%c) = {", c);
        for(i = 0; i < m; i++) {
            printf("%c", f[i]);
            if (i != m - 1) printf(", ");
        }
        printf("}\n");

        // Ask if the user wants to continue
        printf("Continue (1 for Yes, 0 for No)? ");
        scanf("%d%c", &z, &ch); // Read choice to continue or not
    } while(z == 1);
}

void first(char c) {
    int k;
    // If 'c' is a terminal, add it to the FIRST set
    if (!isupper(c)) {
        if (!strchr(f, c)) { // Check if the character is already in the set
            f[m++] = c;
        }
    }

    // If 'c' is a non-terminal, process its productions
    for (k = 0; k < n; k++) {
        if (a[k][0] == c) {
            if (a[k][2] == '$') {
                follow(a[k][0]); // If the production has epsilon, follow the non-terminal
            } else if (islower(a[k][2])) {
                if (!strchr(f, a[k][2])) {
                    f[m++] = a[k][2]; // Add terminal to FIRST
                }
            } else {
                first(a[k][2]); // Recursively call first for non-terminal
            }
        }
    }
}

void follow(char c) {
    // Avoid adding duplicate entries to FOLLOW set
    if (visited[c - 'A']) return;
    visited[c - 'A'] = 1;

    if (a[0][0] == c) {
        f[m++] = '$'; // Add '$' to FOLLOW of start symbol
    }

    // Iterate over all productions
    for (i = 0; i < n; i++) {
        for (j = 2; j < strlen(a[i]); j++) {
            // If the non-terminal 'c' appears in the right-hand side
            if (a[i][j] == c) {
                // If it is not the last character, add FIRST of the next character
                if (a[i][j + 1] != '\0') {
                    first(a[i][j + 1]);
                }

                // If it is the last character or epsilon, add FOLLOW of left-hand side
                if (a[i][j + 1] == '\0' && c != a[i][0]) {
                    follow(a[i][0]);
                }
            }
        }
    }
}