CSE Fall 2015 Section 002 Exam 2, Time: 80 mins

Transcription

1 CSE Fall 2015 Section 002 Exam 2, Time: 80 mins Name:. Student ID:. Total exam points: 100. Question Points Out of Total 100 SOLVE 5 OUT 6 PROBLEMS. You must specify what problem you skipped. If not, problem 6 will the skipped one, and therefore not graded. You cannot receive credit from all 6 problems. If you have the smallest doubt about what a question asks of you, or whether or not you can use certain instructions, ASK US! (Even if you think that it is a really silly question). When asked what the program prints, show what every print instruction prints (even if it is just Bye ) and respect the formatting (print on the same line, or a new line, respect the order of variables, the order in which instructions are executed, and so on). If a problem requires you to write a method and you do not, you automatically lose 50% of the credit for that problem. DO NOT HARDCODE any data in the methods. That is, your methods should work with other data (provided as an argument), not only that shown as an example. Do not use Java instructions not covered in class unless you get permission from the instructor first. You can assume the code below exists for each question. You only need to add your code. import java.util.scanner; public class exam { //The code you write in the programming questions would go here. 1

2 Question 1 (20 points) a) (11 points) What will the following program print? Pay attention to details. public class question1a { public static int foo(int a, int b, int d) { int c = 10; for (int i = a; i < b; i++) { c = c + d; System.out.printf("foo: a = %d\n", a); System.out.printf("foo: b = %d\n", b); System.out.printf("foo: c = %d\n", c); System.out.printf("foo: d = %d\n", d); a = 3; b = 5; c = 7; return c; public static void main(string[] args) { int a = 4; int b = 5; int c = 6; int d = foo(b, c, a); System.out.printf("main: a = %d\n", a); System.out.printf("main: b = %d\n", b); System.out.printf("main: c = %d\n", c); System.out.printf("main: d = %d\n", d); 2

3 b) (6 points) What will the following program print? Pay attention to details. public class question1b { public static void print_array(string name, int[] array){ System.out.printf("%s: ", name); for (int i = 0; i < array.length; i++) { System.out.printf("%d ", array[i]); System.out.printf("\n"); public static void main(string[] args) { int[] a = {4, 5, 6; int[] b = {4, 5, 6; int[] c = a; a[0] = 10; b[1] = 20; c[2] = 30; print_array("a", a); print_array("b", b); print_array("c", c); c) (3 points) What is wrong with the following program? public class question1c { public static void print_array(string name, int[] array){ int[] arr = new[10]; for (int i = 1; i <= 10; i++) { arr[i] = i * i; 3

4 Question 2 (20 points) complete program: method and main Write a method called scale that - takes 2 arguments: an array of integers, arr, and an integer, k, - does not return anything - multiplies each element in arr array by k. For example if arr = {3,0,7,1 and k = 10, it will change arr to be: {30, 0, 70, 10. Finish the main method by adding code to: - call the scale method for the array myarr, and then - print the the modified array (it will print values: 30, 0, 70, 10). DO NOT HARDCODE. Even though the {3,0,7,1 data is used in the example and in main, your code should work for any other array. public class exam { public static void main(string[] args){ //remember to close int[] myarr = {3, 0, 7, 1; // your code here 4

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6 Question 3 (20 points) method only Write a method called evenodd that: - takes one integer argument, N, - returns an array with N integers read from the user - allows the user to enter N integers and places them in the array as follows: o even numbers are placed as leftmost as possible o odd numbers, are placed as rightmost as possible. See below how the array gets populated if evenodd(6) is called and the user gives the following integers (in this order): 10 // after this, the array will have: [10, 0, 0, 0, 0, 0] 3 // after this, the array will have: [10, 0, 0, 0, 0, 3] 7 // after this, the array will have: [10, 0, 0, 0, 7, 3] 2 // after this, the array will have: [10, 2, 0, 0, 7, 3] 4 // after this, the array will have: [10, 2, 4, 0, 7, 3] 11 // after this, the array will have: [10, 2, 4, 11, 7, 3] 6

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8 Question 4 (20 points) complete program: method and main Write a method called areequal that: - takes as arguments two arrays of integers, arr1 and arr2 - returns true if arr1 and arr2 contain the same elements in the same order and false otherwise. For example: If arr1 = {6,0,2,8,1 and arr2 = {6,0,2,8,1 it will return true. If arr1 = {6,0,2,8,1 and arr2 = {6,0,2,8,1, 100 it will return false. If arr1 = {6,0,2,8,1 and arr2 = {6,70,2,8,1 it will return false. If arr1 = {6, 0,2,8,1 and arr2 = {0, 6,2,8,1 it will return false. Hint: check that both arrays have the same value at each index. Finish the main method by adding code to: - create 2 arrays of integers, - call the areequal method for these arrays, and then - using the retuned value, print: equal or NOT equal. public class exam { public static void main(string[] args){ //remember to close // your code here 8

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10 Question 5 (20 points) method only Write a method called select that - takes as argument an array of integers, arr. - returns another array of integers that contains all the values of arr that are less or equal to 100. For example if arr = {3,150,7,1 it will return the array {3, 7, 1(in the same order). You should NOT use Array Lists for this problem. 10

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12 Question 6 (20 points) method only Solve one of the 2 problems below (A or B) A) Write a method called countmax that - takes 2 arguments: an array of strings, strarr, and a character, ch, - returns the MAXIMUM count of occurrences of ch in strings from strarr (notice that strarr has multiple strings in it). You should write your own code to do the count. You should not use any methods provided by Java libraries that count the number of occurrences for you. E.g.: for the array {"a catalog", "arch", "bed", "sun and rain", and ch = 'a', the MAXIMUM count of a in a string is 3 (from the first string). B) Write a method called printto100 that takes no arguments and prints a table of numbers from 1 to 100 as follows: - numbers 1 to 10 inclusive on one row, - 11 to 20 inclusive on the second row - and so on up to 90 to 100 inclusive on the last row. - But, for the diagonal, instead of the numbers (1, 12, 23, 34,,89,100) it prints a star. 12

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