Question

S1I Summer 09 Page 7 Practice Final Exam (30 points) Fill in the blanks to complete the following recursive program It should print a pattern like the one below, using System.out.printin. The argument, lines, says how many lines long the pattern should be. Assume you have a method String nspaces(n) which returns a string containing n spaces. CYou should not write nspaces.) Here is the pattern when lines is 4. The first line VI. name has one space before the **whle the last has 4 spaces before the public static slant(int lines) if s points) Suppose an array has the contents shown below. Suppose we do a binary search for the number 10 in this array. A. circle the elements that would be compared to 10. VII. 6 5 4 3 2 0 index 18 15 10 7 9 4 3 contents B. Which of the numbers in the array above would cause a worst case search if we searched for them? C. In the worst case how many elements of the array would be compared with the number we are searching for? D. Which of the numbers in the array above would cause a best case search if we searched for them? E. In the best case how many elements of the array would be compared with the number we are searching for?

Answer 1

Binary search always works upon sorted array.It is used to find targeted value position in sorted array.To do this with given above array,first we divide an array into two-half by considering middle element 9.

3 4 7 9 10 15 16

Now there are two halves,one is right half and another is left half.

Again we divide the left-half with middle element 4 and right half with 15.

3 4 7 9 10 15 16

So for 4 value we have one element in left-half i.e. 3 and on the left half is 7.

And same for 15 value we have one element in left-half i.e. 10 and on the left half is 16.

Now our targeted value to be searched is 10.

1) first,compare 10 with 9

10<9 = false,search in right half of 9.

2) 10<15=true,search in left half of 15 and hence we'll get the targeted value 10.

B. Elements 3,7,10,16 causes worst case search because to search them first need to compare with middle element 9,then in the right or left half middle element 4 or 15,again in right or left half of 4 and 15 .

C. As stated above to search target value 10 ,compare it with 9,then right half middle element 15.

D. 4,15 are the elements in an array which causes best search.As an array divided into two halves with middle element 9,for the left half we have 4 middle element and in right half we have middle element 15.If we search for 4 then

4<9=true,search left half ,hence we get an element.

E. In the best case search we only need to compare top most middle element with right or left half middle element and that's it.