How to implement the given using only 2 semaphores?

Question

Answer 1

Here P=0 S=1;

P1:                                 P2

wait(P)                            wait(S)

use R1                             use R1

use R2                             signal(P)

signal(S)                          wait(S)

wait(P)                             use R2

use R3                             use R3

use R4                              signal(P)

signal(S)                            wait(S)

                                          Use R4

Answer 2

multiple ways are possible , one of the way is as follow

say 2 semaphores R=0 , S=0

     P1:                                                                  P2:

 wait(R)                                                             USE R1

                                                                        signal(R)

USE R1

USE R2

signal(S)                                                          wait(S)

                                                                      USE R2

                                                                      USE R3

wait(R)                                                             signal(R)

USE R3

USE R4                  

signal(S)                                                          wait(S)

                                                                       USE R4

Answer 3

P->wait, v->signal

P1(){

R2.p()

R4.p()

Critical section

R4.v()

R2.v()

}

​Similar with P1, replacing R2, R4-> R1,R3