str = input string [001]
  |
  |
  V
is_accepted(str)
  |
  |
  V
next_state(t, 0) [t-e,u,e,w;u-1,v;v-1,u;w-0,x;x-0,w]
  |
  |
  V
returns "e:u;e:w;"
  |
  |
  V
next_state(u:0)
  |
  |
  V
returns ""
  |
  |
  V
next_state(w:0)
  |
  |
  V
returns "x:0"
  |
  |
  V
next_state(x:0)
  |
  |
  V
returns "w:0"
  |
  |
  V
next_state(w:1)
  |
  |
  V
returns ""
  |
  |
  V
return false