1. CS1101X: Programming Methodology Recitation 6 Arrays I

2. CS1101X Recitation #62 Task 1: Learning-by-mistake (1/3) A program NonNegativeArray.java to test whether a list of integers contains a negative number is given. The method isNonNegative() returns true if the array contains all non-negative values; it returns false otherwise. 3 5 0 5 10 8 true 9 7 4 12 –3 2 6 false

3. CS1101X Recitation #63 Task 1: Learning-by-mistake (2/3) Which of the following is/are correct? // version 1 public static boolean isNonNegative (int[] arr) { boolean flag = true; for (int i = 0; i < arr.length; ++i) { flag = arr[i] >= 0; } return flag; } // version 2 public static boolean isNonNegative (int[] arr) { boolean flag = true; for (int i = 0; i < arr.length; ++i) { if (arr[i] < 0) flag = false; } return flag; }

4. CS1101X Recitation #64 Task 1: Learning-by-mistake (3/3) Which of the following is/are correct? // version 3 public static boolean isNonNegative (int[] arr) { for (int i = 0; i < arr.length; ++i) { if (arr[i] >= 0) return true; } return false; } // version 4 public static boolean isNonNegative (int[] arr) { for (int i = 0; i < arr.length; ++i) { if (arr[i] < 0) return false; } return true; }

5. CS1101X Recitation #65 Task 2: isSorted A program IsSortedArray.java to test whether a list of integers in sorted in non-decreasing order. The method isSorted() returns true if the array is sorted; it returns false otherwise. 3 5 5 7 18 21 true 1 3 4 7 6 9 11 false

6. CS1101X Recitation #66 Task 3: Second largest Given a list of integers, determine the second largest value in the list. (Assuming that the list contains at least 2 values.) 10 3 7 15 11 2115 5 8 7 9 2 8 1 38 12 7 9 12 10 312

7. CS1101X Recitation #67 Task 4: Pascal’s Triangle (1/3) Blaise Pascal was a scientist, mathematician par excellence who lived in the 17 th century. Some of his mathematical work was fundamental to the theory of probability. There is also a programming language named after him (though in no real sense related to him). More of him in this website (for those who are interested): http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Pascal.html

8. CS1101X Recitation #68 Task 4: Pascal’s Triangle (2/3) In this problem, you are asked to generate Pascal's Triangle. Pascal's Triangle is useful in many areas from probability to polynomials to setting programming questions. It is a triangle of integers with 1 on top and down the sides. Any number in the interior equals the sum of the two numbers above it. For example, here are the first 5 rows of the triangle. 1 11 121 1331 14641

9. CS1101X Recitation #69 Task 4: Pascal’s Triangle (3/3) Write a program to generate a Pascal ’ s Triangle as shown. It should be observed that the next row of the Pascal ’ s triangle can be generated from the previous row. Thus, using an array to store the values of the previous rows seems appropriate. 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 Output for n (number of rows) = 6.

10. CS1101X Recitation #610 To be continued… More problems on arrays (including array of objects) at the next recitation.

11. CS1101X Recitation #611 End of Recitation #6