Hard Multiple Choice Questions¶

These problems are harder than most of those that you will usually see on the AP CS A exam.

7-11-1: Consider the following data field and incomplete method, partialSum, which is intended to return an integer array sum such that for all i, sum[i] is equal to arr + arr + ... + arr[i]. For instance, if arr contains the values {1, 4, 1, 3}, the array sum will contain the values {1, 5, 6, 9}. Which of the following is true about the two implementations of missing code on line 9 that are proposed?

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 private int[] arr; public int[] partialSum() { int[] sum = new int[arr.length]; for (int j = 0; j < sum.length; j++) sum[j] = 0; /* missing code */ return sum; } Implementation 1 for (int j = 0; j < arr.lenth; j++) sum[j] = sum[j - 1] + arr[j]; Implementation 2 for (int j = 0; j < arr.length; j++) for (int k = 0; k <= j; k++) sum[j] = sum [j] + arr[k]; 

7-11-2: A two-dimensional array, imagePixels, holds the brightness values for the pixels in an image. The brightness can range from 0 to 255. What does the following method compute?

  1 2 3 4 5 6 7 8 9 10 11 12 13 public int findMax(int[][] imagePixels) { int r, c; int i, iMax = 0; for (r = 0; r < imagePixels.length; r++) { for (c = 0; c < imagePixels.length; c++) { i = image[r][c]; if (i > iMax) iMax = i; } } return iMax; }