To write a C program for Conversion of Non-Deterministic Finite Automaton (NFA) To Deterministic Finite Automaton (DFA).
Step 1 : Take โ closure for the beginning state of NFA as beginning state of DFA.
Step 2 : Find the states that can be traversed from the present for each input symbol (union of transition value and their closures for each states of NFA present in current state of DFA).
Step 3 : If any new state is found take it as current state and repeat step 2.
Step 4 : Do repeat Step 2 and Step 3 until no new state present in DFA transition table.
Step 5 : Mark the states of DFA which contains final state of NFA as final states of DFA.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LEN 100
char NFA_FILE[MAX_LEN];
char buffer[MAX_LEN];
int zz = 0;
// Structure to store DFA states and their
// status ( i.e new entry or already present)
struct DFA {
char *states;
int count;
} dfa;
int last_index = 0;
FILE *fp;
int symbols;
/* reset the hash map*/
void reset(int ar[], int size) {
int i;
// reset all the values of
// the mapping array to zero
for (i = 0; i < size; i++) {
ar[i] = 0;
}
}
// Check which States are present in the e-closure
/* map the states of NFA to a hash set*/
void check(int ar[], char S[]) {
int i, j;
// To parse the individual states of NFA
int len = strlen(S);
for (i = 0; i < len; i++) {
// Set hash map for the position
// of the states which is found
j = ((int)(S[i]) - 65);
ar[j]++;
}
}
// To find new Closure States
void state(int ar[], int size, char S[]) {
int j, k = 0;
// Combine multiple states of NFA
// to create new states of DFA
for (j = 0; j < size; j++) {
if (ar[j] != 0)
S[k++] = (char)(65 + j);
}
// mark the end of the state
S[k] = '\0';
}
// To pick the next closure from closure set
int closure(int ar[], int size) {
int i;
// check new closure is present or not
for (i = 0; i < size; i++) {
if (ar[i] == 1)
return i;
}
return (100);
}
// Check new DFA states can be
// entered in DFA table or not
int indexing(struct DFA *dfa) {
int i;
for (i = 0; i < last_index; i++) {
if (dfa[i].count == 0)
return 1;
}
return -1;
}
/* To Display epsilon closure*/
void Display_closure(int states, int closure_ar[],
char *closure_table[],
char *NFA_TABLE[][symbols + 1],
char *DFA_TABLE[][symbols]) {
int i;
for (i = 0; i < states; i++) {
reset(closure_ar, states);
closure_ar[i] = 2;
// to neglect blank entry
if (strcmp(&NFA_TABLE[i][symbols], "-") != 0) {
// copy the NFA transition state to buffer
strcpy(buffer, &NFA_TABLE[i][symbols]);
check(closure_ar, buffer);
int z = closure(closure_ar, states);
// till closure get completely saturated
while (z != 100)
{
if (strcmp(&NFA_TABLE[z][symbols], "-") != 0) {
strcpy(buffer, &NFA_TABLE[z][symbols]);
// call the check function
check(closure_ar, buffer);
}
closure_ar[z]++;
z = closure(closure_ar, states);
}
}
// print the e closure for every states of NFA
printf("\n e-Closure (%c) :\t", (char)(65 + i));
bzero((void *)buffer, MAX_LEN);
state(closure_ar, states, buffer);
strcpy(&closure_table[i], buffer);
printf("%s\n", &closure_table[i]);
}
}
/* To check New States in DFA */
int new_states(struct DFA *dfa, char S[]) {
int i;
// To check the current state is already
// being used as a DFA state or not in
// DFA transition table
for (i = 0; i < last_index; i++) {
if (strcmp(&dfa[i].states, S) == 0)
return 0;
}
// push the new
strcpy(&dfa[last_index++].states, S);
// set the count for new states entered
// to zero
dfa[last_index - 1].count = 0;
return 1;
}
// Transition function from NFA to DFA
// (generally union of closure operation )
void trans(char S[], int M, char *clsr_t[], int st,
char *NFT[][symbols + 1], char TB[]) {
int len = strlen(S);
int i, j, k, g;
int arr[st];
int sz;
reset(arr, st);
char temp[MAX_LEN], temp2[MAX_LEN];
char *buff;
// Transition function from NFA to DFA
for (i = 0; i < len; i++) {
j = ((int)(S[i] - 65));
strcpy(temp, &NFT[j][M]);
if (strcmp(temp, "-") != 0) {
sz = strlen(temp);
g = 0;
while (g < sz) {
k = ((int)(temp[g] - 65));
strcpy(temp2, &clsr_t[k]);
check(arr, temp2);
g++;
}
}
}
bzero((void *)temp, MAX_LEN);
state(arr, st, temp);
if (temp[0] != '\0') {
strcpy(TB, temp);
} else
strcpy(TB, "-");
}
/* Display DFA transition state table*/
void Display_DFA(int last_index, struct DFA *dfa_states,
char *DFA_TABLE[][symbols]) {
int i, j;
printf("\n\n********************************************************\n\n");
printf("\t\t DFA TRANSITION STATE TABLE \t\t \n\n");
printf("\n STATES OF DFA :\t\t");
for (i = 1; i < last_index; i++)
printf("%s, ", &dfa_states[i].states);
printf("\n");
printf("\n GIVEN SYMBOLS FOR DFA: \t");
for (i = 0; i < symbols; i++)
printf("%d, ", i);
printf("\n\n");
printf("STATES\t");
for (i = 0; i < symbols; i++)
printf("|%d\t", i);
printf("\n");
// display the DFA transition state table
printf("--------+-----------------------\n");
for (i = 0; i < zz; i++) {
printf("%s\t", &dfa_states[i + 1].states);
for (j = 0; j < symbols; j++) {
printf("|%s \t", &DFA_TABLE[i][j]);
}
printf("\n");
}
}
// Driver Code
int main() {
int i, j, states;
char T_buf[MAX_LEN];
// creating an array dfa structures
struct DFA *dfa_states = malloc(MAX_LEN * (sizeof(dfa)));
states = 6, symbols = 2;
printf("\n STATES OF NFA :\t\t");
for (i = 0; i < states; i++)
printf("%c, ", (char)(65 + i));
printf("\n");
printf("\n GIVEN SYMBOLS FOR NFA: \t");
for (i = 0; i < symbols; i++)
printf("%d, ", i);
printf("eps");
printf("\n\n");
char *NFA_TABLE[states][symbols + 1];
// Hard coded input for NFA table
char *DFA_TABLE[MAX_LEN][symbols];
strcpy(&NFA_TABLE[0][0], "FC");
strcpy(&NFA_TABLE[0][1], "-");
strcpy(&NFA_TABLE[0][2], "BF");
strcpy(&NFA_TABLE[1][0], "-");
strcpy(&NFA_TABLE[1][1], "C");
strcpy(&NFA_TABLE[1][2], "-");
strcpy(&NFA_TABLE[2][0], "-");
strcpy(&NFA_TABLE[2][1], "-");
strcpy(&NFA_TABLE[2][2], "D");
strcpy(&NFA_TABLE[3][0], "E");
strcpy(&NFA_TABLE[3][1], "A");
strcpy(&NFA_TABLE[3][2], "-");
strcpy(&NFA_TABLE[4][0], "A");
strcpy(&NFA_TABLE[4][1], "-");
strcpy(&NFA_TABLE[4][2], "BF");
strcpy(&NFA_TABLE[5][0], "-");
strcpy(&NFA_TABLE[5][1], "-");
strcpy(&NFA_TABLE[5][2], "-");
printf("\n NFA STATE TRANSITION TABLE \n\n\n");
printf("STATES\t");
for (i = 0; i < symbols; i++)
printf("|%d\t", i);
printf("eps\n");
// Displaying the matrix of NFA transition table
printf("--------+------------------------------------\n");
for (i = 0; i < states; i++) {
printf("%c\t", (char)(65 + i));
for (j = 0; j <= symbols; j++) {
printf("|%s \t", &NFA_TABLE[i][j]);
}
printf("\n");
}
int closure_ar[states];
char *closure_table[states];
Display_closure(states, closure_ar, closure_table, NFA_TABLE, DFA_TABLE);
strcpy(&dfa_states[last_index++].states, "-");
dfa_states[last_index - 1].count = 1;
bzero((void *)buffer, MAX_LEN);
strcpy(buffer, &closure_table[0]);
strcpy(&dfa_states[last_index++].states, buffer);
int Sm = 1, ind = 1;
int start_index = 1;
// Filling up the DFA table with transition values
// Till new states can be entered in DFA table
while (ind != -1) {
dfa_states[start_index].count = 1;
Sm = 0;
for (i = 0; i < symbols; i++) {
trans(buffer, i, closure_table, states, NFA_TABLE, T_buf);
// storing the new DFA state in buffer
strcpy(&DFA_TABLE[zz][i], T_buf);
// parameter to control new states
Sm = Sm + new_states(dfa_states, T_buf);
}
ind = indexing(dfa_states);
if (ind != -1)
strcpy(buffer, &dfa_states[++start_index].states);
zz++;
}
// display the DFA TABLE
Display_DFA(last_index, dfa_states, DFA_TABLE);
return 0;
}
The program was sucessfully converted from NFA to DFA.