A call center agent has a list of 305 phone numbers of people in alphabetic order of names (but she does not have any of the names). She needs to quickly contact Deepak Sharma to convey a message to him. If each call takes 2 minutes to complete, and every call is answered, what is the minimum amount of time in which she can guarantee to deliver the message to Mr Sharma.
a. 18 minutes
b. 610 minutes
c. 206 minutes
d. 34 minutes
Sol: Option A

• 18 min. Here all the mobiles are in alphabetical order without names. So we choose middle number say., 152 or 153 and ask the persons name. If his name is Farookh, then we disregard the numbers 153/154 to 305 as Deepak falls before Farookh. Again we call 71 or 72. If the name is cindy, Then Deepak falls after that. So we disregard 1 to 71/72. So we take a number between 71 to 152 and follow the same procedure. As 305 < 2^9, At the most we can do 9 calls to determine his correct mobile number.
• 10 years agoHelpfull: Yes(20) No(2)
• Use binary search method.
  
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