Hey Pooja,
I have solved it. Need the solution? Here it goes:
SOLUTION:
P = POLICE / T = THIEF / F = FATHER / M = MOTHER / D = DAUGHTER & S = SON
01) P & T cross first
02) P comes back
03) P & D1 cross
04) P & T come back
05) M & D2 cross
06) M comes back
07) M & F cross
08) F comes back
09) P & T cross
10) M comes back
11) M & F cross
12) F comes back
13) F & S1 cross
14) P & T come back
15) P & S2 cross
16) P comes back
17) P & T cross and all REACH SAFELY
From move no. 3, it can be son or daughter, and accordingly, father and mother move.
Regards,
Tushar