GATE | GATE CS 1999 | Question 3

The number of binary strings of n zeros and k ones such that no two ones are adjacent is:

(A) a
(B) b
(C) c
(D) d


Answer: (D)

Explanation: There are n zeros placed :

_0_0_0_….._0_

So, (n+1) gaps. Now we can place k 1’s in those place n+1Ck ways.

Option (D) is correct.

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