Q. If Java did not have a Queue implementation, how would you go about implementing your own? A. A queue can be implemented in a similar fashion to a stack by declaring a backingArray, a frontIndex, a backIndex, and a currentSize. Initialize the frontIndex to 0 and the backIndex to...
Q. Is there a more efficient sorting algorithm than bubble sorting? A. Although bubble-sort is one of the simplest sorting algorithms, it’s also one of the slowest. It has the O(n2) time complexity. Faster algorithms include quick-sort and heap-sort. The Arrays.sort( ) method uses the quick-sort algorithm, … Read more...
Q1. Can you write a sample code that will count the number of “A”s in a given text? Show iterative, recursive, and tail recursive approaches?
“AAA rating”
A1.
Iteration
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public class Iteration { public int countA(String input) { if (input == null || input.length( ) == 0) { return 0; } int count = 0; for (int i = 0; i < input.length( ); i++) { if(input.substring(i, i+1).equals("A")){ count++; } } return count; } public static void main(String[ ] args) { System.out.println(new Iteration( ).countA("AAA rating")); // Ans.3 } } |
Recursion
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public class RecursiveCall { public int countA(String input) { // exit condition – recursive calls must have an exit condition if (input == null || input.length( ) == 0) { return 0; } int count = 0; //check first character of the input if (input.substring(0, 1).equals("A")) { count = 1; } //recursive call to evaluate rest of the input //(i.e. 2nd character onwards) return count + countA(input.substring(1)); } public static void main(String[ ] args) { System.out.println(new RecursiveCall( ).countA("AAA rating")); // Ans. 3 } } |
Many find it harder to understand recursion,
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Q. How will you partition the following numbers 7 3 6 8 2 9 5 4 around the pivotal number of 5 so that the lower values are in front of it and higher values are behind it? A. A single pointer can be used by moving from left to...
Q. You need to sort an array of integers by repeatedly reversing the order of the first several elements of it. you always have to flip from the beginning element, you cannot flip elements 2 and 3. For example, input: [10,30,20] [10,30,20] –> … Read more ›...
Q. If Java did not have a Stack implementation, how would you go about implementing your own? A. Determine the backing data structure (e.g. array, linked list, etc). Determine the methods that need to be implemented like pop( ), push( ), … Read more ›...
Q1. Can you write an algorithm to swap two values? A1.
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package algorithms; public class Swap { public static void main(String[ ] args) { int x = 5; int y = 6; //store 'x' in a temp variable int temp = x; x = y; y = temp; System.out.println("x=" + x + ",y=" + y); } } |
Swapping without a temp variable
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package algorithms; public class Swap { public static void main(String[ ] args) { int x = 5; int y = 6; //without using a temp variable x = x + y; // 11 y = x - y; // 5 x = x - y; //6 System.out.println("x=" + x + ",y=" + y); } } |
Note: also try with * and \ Using bitwise “xor”
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package algorithms; public class Swap { public static void main(String[ ] args) { int x = 5; int y = 6; //without using a temp variable //^ is xor 0 ^ 0 = 0, 0 ^ 1 = 1, 1 ^ 0 = 1, 0 ^ 0 = 0 x = x ^ y; // 3 y = x ^ y; // 5 x = x ^ y; //6 System.out.println("x=" + x + ",y=" + y); } } |
Q2. … Read more ›...
Q1. Can you write an algorithm in Java to swap two variables? A1.
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public class Swap { public static void main(String[ ] args) { int x = 5; int y = 6; //store 'x' in a temp variable int temp = x; x = y; y = temp; System.out.println("x=" + x + ",y=" + y); } } |
Q2. Can you write an algorithm to bubble sort the following array { 30, 12, 18, 0, -5, 72, 424 }?? … Read more ›...
Q. How will you partition the following numbers 7 3 6 8 2 9 5 4 around the pivotal number of 5 so that the lower values are in front of it and higher values are behind it? The pointers are shown with: “^” … Read more ›...
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