Algorithms | Searching | Question 6

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. }

In the above question, the correction needed in the program to make it work properly is (GATE CS 2008)

(A)

Change line 6 to: if (Y[k] < x) i = k + 1; else j = k-1;

(B)

Change line 6 to: if (Y[k] < x) i = k – 1; else j = k+1;

(C)

Change line 6 to: if (Y[k] <= x) i = k; else j = k;

(D)

Change line 7 to: } while ((Y[k] == x) && (i < j));

Answer: (A)
Explanation:

Below is the corrected function 

f(int Y[10], int x) {
   int i, j, k;
   i = 0; j = 9;
   do {
           k =  (i + j) /2;
           if( Y[k] < x)  i = k + 1; else j = k - 1;
       } while(Y[k] != x && i < j);
   if(Y[k] == x) printf (\"x is in the array \") ;
   else printf (\" x is not in the array \") ;
}

Reference: http://en.wikipedia.org/wiki/Binary_search_algorithm#Implementations

Hence Option(A) is the correct option.

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