Untitled

%{
#include <stdio.h>
int state = 0; // Declare state variable
%}

%%

start           { state = 0; }

"a"             { 
                    if (state == 0) state = 1; 
                    else if (state == 1 || state == 2 || state == 3 || state == 4) state = 1; 
                }
"b"             { 
                    if (state == 0) state = 0; 
                    else if (state == 1) state = 2; 
                    else if (state == 2 || state == 3) state = 0; 
                    else if (state == 4) state = 4; 
                }
"ab"            { 
                    if (state == 1) state = 2; 
                    else if (state == 2 || state == 3) state = 3; 
                    else if (state == 4) state = 4; 
                }
"abb"           { 
                    if (state == 3) state = 4; 
                }

\n              { printf("Input accepted\n"); state = 0; }
.               { printf("Input rejected\n"); state = 0; }

%%

int main() {
    yylex();
    return 0;
}