GATE | GATE CS 1996 | Question 66
Consider the following program that attempts to locate an element x in a sorted array a[ ] using binary search. Assume N>1. The program is erroneous. Under what conditions does the program fail?
var i,j,k: integer; x: integer;
a: array; [1....N] of integer;
begin i:= 1; j:= N;
repeat
k:(i+j) div 2;
if a[k] < x then i:= k
else j:= k
until (a[k] = x) or (i >= j);
if (a[k] = x) then
writeln (\'x is in the array\')
else
writeln (\'x is not in the array\')
end;
(A)
x is the last element of the array a[]
(B)
x is greater than all elements of the array a[]
(C)
Both of the Above
(D)
x is less than the last element of the array a[]
Answer: (C)
Explanation:
The above program doesn’t work for the cases where element to be searched is the last element of a[] or greater than the last element (or maximum element) in a[]. For such cases, the program goes in an infinite loop because i is assigned a value as k in all iterations, and i never becomes equal to or greater than j. So while the condition never becomes false.
Hence Option(C) is correct.
Quiz of this Question
Please comment below if you find anything wrong in the above post
Last Updated :
24 Mar, 2019
Like Article
Save Article
Share your thoughts in the comments
Please Login to comment...