Pattern bonding problem Let $\Sigma  = {1,2,3,4}$  . We say that symbol $\sigma $ bonds with
  symbol $\tau$  if $\sigma = \tau$ of $\sigma = \tau +1$ for even
  $\sigma$ and $\sigma = \tau -1$ for odd $\sigma$ . In other words  , 1
  and 2 bond  , and 3 and 4 bond (in addition to every number bonding
  with itself ) . 
  
  The  Pattern bonding problem is defined as follows:
  
  INPUT :  Text $ T = t_{1}  , ..., t_{n}$  and pattern $ P = p_{1}  ,
 ..., p_{m}$ over alphabet  $\Sigma  $ . 
  
  OUTPUT :  All locations $i$ in the text that bond with the pattern , 
  i.e  , where $t_{i+j-1}$ bonds with $p_{j}$ $j=1,...,m$ .


Can someone supply an algorithm for the pattern bonding problem (the faster the better   complexity can)  ?  , I thought about "Less then matching" .  

Edit: (Answer)

Map $ (1,2) \rightarrow \alpha , (3,4)\rightarrow  \beta$ then the text and the pattern is on $\Sigma = {\alpha , \beta}$ and then we know to solve it in $O(n)$ using witness or KMP .
Hint: map $1,2$ to $a$ and $3,4$ to $b$.