Practice 70 Java Stack Programming Questions

Practice 70 Java Stack Programming Questions

Q1. Write a Java program to implement a stack using arrays.
  - Input: Push(10), Push(20), Pop()
  - Expected Output: 20

Q2. Write a Java program to implement a stack using linked list.
  - Input: Push(10), Push(20), Push(30), Pop()
  - Expected Output: 30

Q3. Write a Java program to check if a given string has balanced parentheses using a stack.
  - Input: "(a+b)*(c+d)"
  - Expected Output: True

Q4. Write a Java program to reverse a string using a stack.
  - Input: "hello"
  - Expected Output: "olleh"

Q5. Write a Java program to evaluate a postfix expression using a stack.
  - Input: "5 6 + 7 *"
  - Expected Output: 77

Q6. Write a Java program to evaluate a prefix expression using a stack.
  - Input: "* + 5 6 7"
  - Expected Output: 77

Q7. Write a Java program to implement a stack using Java's `Stack` class.
  - Input: Push(10), Push(20), Push(30), Pop()
  - Expected Output: 30

Q8. Write a Java program to check if a given expression has balanced brackets using a stack.
  - Input: "{[()()]}"
  - Expected Output: True

Q9. Write a Java program to implement a stack and perform push, pop, and peek operations.
  - Input: Push(10), Push(20), Peek(), Pop()
  - Expected Output: 20, 10

Q10. Write a Java program to implement a stack and find the minimum element in the stack.
   - Input: Push(10), Push(5), Push(20)
   - Expected Output: 5

Q11. Write a Java program to check if a given number is a palindrome using a stack.
   - Input: "12321"
   - Expected Output: True

Q12. Write a Java program to convert an infix expression to postfix using a stack.
   - Input: "(a+b)*c"
   - Expected Output: "ab+c*"

Q13. Write a Java program to convert an infix expression to prefix using a stack.
   - Input: "(a+b)*c"
   - Expected Output: "*+abc"

Q14. Write a Java program to implement a stack that supports min() in O(1) time.
   - Input: Push(10), Push(5), Push(20)
   - Expected Output: 5

Q15. Write a Java program to implement a stack and check if an array is a stack permutation of another array.
   - Input: [1, 2, 3], [2, 1, 3]
   - Expected Output: True

Q16. Write a Java program to reverse the elements of a stack.
   - Input: Push(1), Push(2), Push(3), Pop()
   - Expected Output: 1, 2, 3

Q17. Write a Java program to sort a stack using recursion.
   - Input: Push(3), Push(1), Push(2)
   - Expected Output: 1, 2, 3

Q18. Write a Java program to implement a stack using two queues.
   - Input: Push(10), Push(20), Pop()
   - Expected Output: 20

Q19. Write a Java program to check if a sequence of stack operations is valid.
   - Input: Push(1), Push(2), Pop(), Pop()
   - Expected Output: True

Q20. Write a Java program to implement a stack and find the maximum element in the stack.
   - Input: Push(10), Push(20), Push(5)
   - Expected Output: 20

Q21. Write a Java program to implement a stack using two stacks.
   - Input: Push(10), Push(20), Pop()
   - Expected Output: 20

Q22. Write a Java program to count the number of elements in a stack.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 3

Q23. Write a Java program to implement a stack using an array and find the middle element.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 20

Q24. Write a Java program to implement a stack and check if it is empty.
   - Input: Push(10), Pop()
   - Expected Output: True

Q25. Write a Java program to implement a stack and pop the first element.
   - Input: Push(10), Push(20), Pop()
   - Expected Output: 20

Q26. Write a Java program to implement a stack and find the top element.
   - Input: Push(10), Push(20), Peek()
   - Expected Output: 20

Q27. Write a Java program to implement a stack and perform operations of push, pop, and peek.
   - Input: Push(5), Pop(), Peek()
   - Expected Output: None, 5

Q28. Write a Java program to implement a stack that supports push, pop, peek, and size operations.
   - Input: Push(10), Push(20), Size()
   - Expected Output: 2

Q29. Write a Java program to implement a stack that supports push, pop, peek, size, and min operations.
   - Input: Push(10), Push(20), Min()
   - Expected Output: 10

Q30. Write a Java program to implement a stack and print elements in reverse order.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 30, 20, 10

Q31. Write a Java program to reverse the words in a sentence using a stack.
   - Input: "Hello World"
   - Expected Output: "World Hello"

Q32. Write a Java program to check if parentheses in an expression are balanced using a stack.
   - Input: "[{()}]"
   - Expected Output: True

Q33. Write a Java program to reverse a stack using recursion.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 30, 20, 10

Q34. Write a Java program to implement a stack and push an element at the bottom.
   - Input: Push(10), Push(20), BottomPush(5)
   - Expected Output: 5, 10, 20

Q35. Write a Java program to implement a stack and pop an element from the bottom.
   - Input: Push(10), Push(20), BottomPop()
   - Expected Output: 10

Q36. Write a Java program to implement a stack and perform push, pop, and display operations.
   - Input: Push(5), Pop(), Display()
   - Expected Output: Empty Stack

Q37. Write a Java program to find the sum of elements in a stack.
   - Input: Push(5), Push(10), Push(15)
   - Expected Output: 30

Q38. Write a Java program to find the product of elements in a stack.
   - Input: Push(5), Push(10), Push(2)
   - Expected Output: 100

Q39. Write a Java program to find the second largest element in a stack.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 20

Q40. Write a Java program to implement a stack that can hold only even numbers.
   - Input: Push(2), Push(4), Push(3)
   - Expected Output: 2, 4

Q41. Write a Java program to implement a stack and perform push and pop operations using user input.
   - Input: Push(10), Pop()
   - Expected Output: 10

Q42. Write a Java program to implement a stack and perform push and pop operations using an integer array.
   - Input: Push(5), Push(10), Pop()
   - Expected Output: 10

Q43. Write a Java program to implement a stack and find the sum of the first n elements.
   - Input: Push(10), Push(20), Push(30), Sum()
   - Expected Output: 60

Q44. Write a Java program to implement a stack and print the elements from top to bottom.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 30, 20, 10

Q45. Write a Java program to implement a stack and reverse the stack in-place.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 30, 20, 10

Q46. Write a Java program to implement a stack and display the stack after each operation.
   - Input: Push(10), Push(20), Pop()
   - Expected Output: 10, 20, 10

Q47. Write a Java program to implement a stack and remove all elements.
   - Input: Push(10), Push(20), Clear()
   - Expected Output: Empty Stack

Q48. Write a Java program to check if a stack is full.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: Full

Q49. Write a Java program to implement a stack with the ability to get the current size.
   - Input: Push(10), Push(20), Size()
   - Expected Output: 2

Q50. Write a Java program to implement a stack that supports the operation to get the top element.
   - Input: Push(10), Push(20), Top()
   - Expected Output: 20

Q51. Write a Java program to implement a stack and find the depth of a stack.
   - Input: Push(10), Push(20), Depth()
   - Expected Output: 2

Q52. Write a Java program to implement a stack and check if it is full or empty.
   - Input: Push(10), Push(20), Full()
   - Expected Output: False

Q53. Write a Java program to implement a stack and calculate the sum of elements at even positions.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 40

Q54. Write a Java program to implement a stack and calculate the sum of elements at odd positions.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 30

Q55. Write a Java program to implement a stack and find the frequency of each element.
   - Input: Push(10), Push(10), Push(20)
   - Expected Output: 10 -> 2, 20 -> 1

Q56. Write a Java program to implement a stack and calculate the product of elements at odd positions.
   - Input: Push(5), Push(10), Push(15)
   - Expected Output: 75

Q57. Write a Java program to implement a stack and perform multiple push and pop operations.
   - Input: Push(10), Pop(), Push(20), Push(30), Pop()
   - Expected Output: 10, 30

Q58. Write a Java program to implement a stack and check if the stack is a palindrome.
   - Input: Push(1), Push(2), Push(1)
   - Expected Output: True

Q59. Write a Java program to implement a stack and check if the stack is sorted.
   - Input: Push(1), Push(2), Push(3)
   - Expected Output: Sorted

Q60. Write a Java program to implement a stack and push elements in reverse order.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 30, 20, 10

Q61. Write a Java program to implement a stack and find the average of all elements.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 20

Q62. Write a Java program to implement a stack and perform pop until the stack is empty.
   - Input: Push(10), Push(20), Pop(), Pop()
   - Expected Output: 20, 10

Q63. Write a Java program to implement a stack and check if an element exists in the stack.
   - Input: Push(10), Push(20), Contains(20)
   - Expected Output: True

Q64. Write a Java program to implement a stack and swap the top two elements.
   - Input: Push(10), Push(20), Swap()
   - Expected Output: 20, 10

Q65. Write a Java program to implement a stack and push elements alternately.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 10, 20, 30

Q66. Write a Java program to implement a stack and pop elements alternately.
   - Input: Push(10), Push(20), Pop(), Pop()
   - Expected Output: 20, 10

Q67. Write a Java program to implement a stack and print elements using recursion.
   - Input: Push(1), Push(2), Push(3)
   - Expected Output: 3, 2, 1

Q68. Write a Java program to implement a stack and check if the stack is empty.
   - Input: Push(10), Pop(), IsEmpty()
   - Expected Output: True

Q69. Write a Java program to implement a stack and count the occurrences of a specific element.
   - Input: Push(10), Push(20), Push(10), Count(10)
   - Expected Output: 2

Q70. Write a Java program to implement a stack and find the median element.
   - Input: Push(10), Push(20), Push(30)
   - Expected Output: 20