20. What are the contents of the array nums after the following code segment has been executed?

    int[] nums = new int[8]; nums[0] = 0; int n = 1; while (n < nums.length) { int k; for (k = n; k < 2*n; k++) nums[k] = nums[k-n] + 1; n = k; }

    1. 0 1 1 1 1 1 1 1

    2. 0 1 0 1 0 1 0 1

    3. 0 1 1 2 1 2 2 3

    4. 0 1 2 3 1 2 3 4

    5. 0 1 2 3 4 5 6 7

    Question 20 ABCDE

21. Consider the following method.

    /** Rearranges the elements in words according to * the values stored in an integer array indices * so that the element of words at index indices[k] * is moved to the element at index k. * Precondition: words.size() == indices.length */ public void permute(List words, int[] indices) { ArrayList temp = new ArrayList(); < missing code > }

    For example, after executing the code segment

    List words = new ArrayList(); words.add("I"); words.add("am"); words.add("Sam"); int[] indices = {2, 0 1}; permute(words, indices);

    words will become the list ["Sam", "I", "am"]. Which of the following code segments could replace <missing code> in the permute method?

    	for (String word : words) temp.add(word); for (int k = 0; k < indices.length; k++) words.set(k, temp.get(indices[k]));
    	for (int j : indices) temp.add(words.get(j)); for (int k = 0; k < indices.length; k++) words.set(k, temp.get(k));
    	while (words.size() > 0) temp.add(words.remove(0)); for (int j : indices) words.add(temp.get(j));

    1. I only

    2. II only

    3. I and II only

    4. II and III only

    5. I, II, and III

    Question 21 ABCDE

22. What is printed as a result of executing the following code segment?

    ArrayList digits = new ArrayList(); for (int k = 0; k <= 9; k++) digits.add("" + k); for (int k = 0; k <= 4; k++) { String d1 = digits.remove(k); String d2 = digits.remove(k); digits.add(k, d1 + "+" + d2); } System.out.println(digits);

    1. [0+1, 1+2, 2+3, 3+4, 4+5]

    2. [0+1, 2+3, 4+5, 6+7, 8+9]

    3. [0+1, 1+2, 2+3, 3+4, 5, 6, 7, 8, 9]

    4. [0+1, 1+2, 2+3, 3+4, 4+5, 6, 7, 8, 9]

    5. [0+0, 1+1, 2+2, 3+3, 4+4, 5, 6, 7, 8, 9]

    Question 22 ABCDE

23. Consider the following method.

    /** Returns the number of zeroes in s. * Precondition: s.length() = 31; s holds several * 0's followed by several 1's * (s can also be all 0's or all 1's) */ public int countZeroes(String s) { int i = 0, j = 30; while (i <= j) { int k = (i + j) / 2; if (s.substring(k, k+1).equals("0")) i = k + 1; else j = k - 1; } return i: }

    How many iterations through the while loop will be made in the best and the worst case?

    	Best case		Worst case
    	1		5
    	1		15
    	4		5
    	4		15
    	5		5