Using Double Ended Queues (Deques) for Transpose Sequences

This is an interesting question that may be more interesting than helpful. Let's say I want to copy two of its comment ( DQ1_a

and DQ1_b

) in the copies ( DQ2_a

and DQ2_b

).

DQ1_a= <A,B,C,D,E,F>
DQ1_b= <G,H,I,J,K,L,M>   

      

        
        
        
      

    

But we want to exchange "strands" for D<->J

. Thus, we want to get

DQ2_a= <A,B,C,(D or J),K,L,M>
DQ2_b= <G,H,I,(J or D),E,F>

      

        
        
        
      

    

or

exists because it depends on whether it includes elements denoting an exchange or not.

Question 1

: Find the algorithm that ends up with the transposed data structure DQ2_*

, starting with the score data DQ1_*

and the items exchanged ex=(D<->J); ex[a]=D; ex[b]=J

. Allowed operations are deque - left_push,left_pop,right_push,right_pop,deque_empty

(the latter returns whether empty or not).

Decision:

left_item  <- left_pop(DQ1_a)
while (left_item!=ex[a]):
  right_push(DQ2_a,left_item)
  left_item<-left_pop(DQ1_a)

right_item <- right_pop(DQ1_b)
while (right_item!=ex[b]):
  left_push(DQ2_b,right_item)
  right_item<-right_pop(DQ1_b)

# if not inclusive
right_push(DQ2_a,left_item)
left_push(DQ2_b,right_item)
# else 
#right_push(DQ2_b,left_item)
#left_push(DQ2_a,right_item)

left_item  <- left_pop(DQ1_b)
while (not deque_empty(DQ1_b)):
  right_push(DQ2_a,left_item)
  left_item<-left_pop(DQ1_a)

right_item <- right_pop(DQ1_a)
while (not deque_empty(DQ1_a)):
  left_push(DQ2_b,right_item)
  right_item<-rightt_pop(DQ1_a)

      

        
        
        
      

    

Question 2

: This is what hits me. Given a set DQ1_*

(more than 2) - you need to copy them to DQ2_*

using the exchange list

ex={s: s is a given set of exchanges of the form: (ith element of DQ1_x)<->(jth element of DQ1_y)}

      

        
        
        
      

    

Any better solutions to this problem are appreciated!