Consider the following C program that attempts to locate an element x in an array Y[] using binary search. The program is erroneous. (GATE CS 2008)
C
1. f(int Y[10], int x) {2. int i, j, k;3. i = 0; j = 9;4. do {5. k = (i + j) /2;6. if( Y[k] < x) i = k; else j = k;7. } while(Y[k] != x && i < j);8. if(Y[k] == x) printf (\"x is in the array \") ;9. else printf (\" x is not in the array \") ;10. } |
On which of the following contents of Y and x does the program fail?
(A)
Y is [1 2 3 4 5 6 7 8 9 10] and x < 10
(B)
Y is [1 3 5 7 9 11 13 15 17 19] and x < 1
(C)
Y is [2 2 2 2 2 2 2 2 2 2] and x > 2
(D)
Y is [2 4 6 8 10 12 14 16 18 20] and 2 < x < 20 and x is even
Answer: (C)
Explanation:
The above program doesn’t work for the cases where the element to be searched is the last element of Y[] or greater than the last element (or maximum element) in Y[]. For such cases, the program goes in an infinite loop because i is assigned 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 the correct option.
Quiz of this Question
Please comment below if you find anything wrong in the above post