===== nfa_closure.c =====

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

char result[20][20], copy[3], states[20][20];

void add_state(char a[3], int i) {
    strcpy(result[i], a);
}

void display(int n) {
    int k = 0;
    printf("\nEpsilon closure of %s = { ", copy);
    while (k < n) {
        printf(" %s", result[k]);
        k++;
    }
    printf(" }\n");
}

int main() {
    int n, t;   // n = number of states, t = number of transitions
    int i, k;

    char state[3], state1[3], input[3], state2[3];

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

    printf("Enter the states:\n");
    for (k = 0; k < n; k++) {
        scanf("%s", states[k]);
    }

    printf("Enter the number of transitions: ");
    scanf("%d", &t);

    char trans_from[20][3], trans_input[20][3], trans_to[20][3];

    printf("Enter transitions in the form <from> <input> <to>\n");
    printf("(use 'e' for epsilon):\n");
    for (i = 0; i < t; i++) {
        scanf("%s %s %s", trans_from[i], trans_input[i], trans_to[i]);
    }

    // compute epsilon closure for each state
    for (k = 0; k < n; k++) {
        int count = 0;
        strcpy(state, states[k]);
        strcpy(copy, state);
        add_state(state, count++);

        int changed = 1;
        while (changed) {
            changed = 0;
            for (i = 0; i < t; i++) {
                if (strcmp(state, trans_from[i]) == 0 && strcmp(trans_input[i], "e") == 0) {
                    add_state(trans_to[i], count++);
                    strcpy(state, trans_to[i]);
                    changed = 1;
                }
            }
        }
        display(count);
    }

    return 0;
}

===== run =====
nano nfa_closure.c
gcc nfa_closure.c -o nfa_closure
./nfa_closure