Regular Expression

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

int main(){

    char text[256];
    int i, length, error, no_rule;

    /*
    Rule 1: a*b
    Rule 2: ab+
    Rule 3: abb
    */

repeat:
    i = 0;
    length = 0;
    error = 0;
    no_rule = 1;


    printf("Enter Text: ");
    scanf("%[^\n]s", text);
    length = strlen(text);

    if(strcmp(text, ";") == 0){
        return 0;
    }

    if(length > 0){
        if((text[0] == 'a' || text[0] == 'b') && text[length-1] == 'b'){
            error == 0;
            for(i = 1; i < length - 1; i++){
                if(text[i] != 'a'){
                    error = 1;
                    break;
                }
            }
            if(error == 0){
                printf("\nUnder Rule 1");
                no_rule = 0;
            }
        }

        if(text[0] == 'a' && text[1] == 'b'){
            error = 0;
            for(i = 1; i < length; i++){
                if(text[i] != 'b'){
                    error = 1;
                    break;
                }
            }
            if(error == 0){
                printf("\nUnder Rule 2");
                no_rule = 0;
            }
        }

        if(strcmp(text, "abb") == 0){
            printf("\nUnder Rule 3");
            no_rule = 0;
        }

        if(no_rule == 1){
            printf("\nUnder no rule!");
        }
    }

    printf("\n\n");

    fflush(stdin);
    goto repeat;
    return 0;
}