000

#include <stdio.h>
#include "myregex.h"
#define MAXCHAR 256

int fsm(char s[])
{
int state = 1;
int i = 0;
while(1)
{
switch( state )
{

case 1:
if(s[i] == 'a')
{
state = 2;
i++;
break;
}
else if(s[i] == 'b')
{
state = 3;
i++;
break;
}
else{
printf("no.");
return 0;
break;
}

case 2:
if(s[i] == 'a')
{
state = 2;
i++;
break;
}
else if(s[i] == 'b')
{
state = 4;
i++;
break;
}
else
{
printf("no.");
return 0;
break;
}

case 3:
if(s[i] == 'b')
{
state = 3;
i++;
break;
}
else if(s[i] == 'a')
{
state = 2;
i++;
break;
}
else
{
printf("no.");
return 0;
break;
}

case 4:
if(s[i] == 'a')
{
state = 2;
i++;
break;
}
else if(s[i] == 'b')
{
state = 5;
i++;
break;
}
else
{
printf("no.");
return 0;
break;
}

case 5:
if(s[i] == 'a')
{
state = 2;
i++;
break;
}
else if(s[i] == 'b')
{
state = 3;
i++;
break;
}
else if(s[i] == '\0')
{
state = 6;
break;
}
else
{
printf("no.");
return 0;
break;
}

case 6:
printf("yes.");
return 0;
break;

}
}
}

main()
{
char s[MAXCHAR];
printf("Input a string:\n");
gets(s);
fsm(s);
}