41. Write a function to simulate a stack underflow.
42. Implement a function to display the contents of a stack.
43. Write a function to find the intersection of two stacks.
44. Implement a function to find the union of two stacks.
45. Write a function to reverse a linked list using a stack.
46. Implement a function to duplicate a stack.
47. Write a function to implement a priority stack.
48. Implement a function to convert postfix expressions to infix expressions using a stack.
49. Write a function to check for anagrams using a stack.
50. Implement a function to find the longest valid parentheses substring using a stack.
51. Write a function to generate valid parentheses combinations using a stack.
52. Implement a function to implement a min stack with O(1) time complexity.
53. Write a function to push and pop in a single stack simultaneously.
54. Implement a function to find the middle element of a stack.
55. Write a function to implement a stack that can store multiple data types.
56. Implement a function to pop the Nth element from the stack.
57. Write a function to push an array of elements onto a stack.
58. Implement a function to remove the bottom element from a stack.
59. Write a function to implement a stack that logs all operations.
60. Implement a function to check if a stack is sorted.
61. Write a function to retrieve elements from a stack in sorted order.
62. Implement a function to find the kth smallest element in a stack.
63. Write a function to implement a stack that returns the maximum element efficiently.
64. Implement a function to check if a stack contains a certain element.
65. Write a function to swap the top two elements of the stack.
66. Implement a function to insert an element at the bottom of the stack.
67. Write a function to reverse the order of elements in a stack.
68. Implement a function to clone a stack.
69. Write a function to calculate the size of a stack in O(1) time.
70. Implement a function to rotate the stack elements.
71. Write a function to create a stack of integers and perform basic operations.
72. Implement a function to display stack elements from top to bottom.
73. Write a function to check if the stack is a palindrome.
74. Implement a function to perform a breadth-first search (BFS) using a stack.
75. Write a function to compare two stacks for equality.
76. Implement a function to push unique elements onto a stack.
77. Write a function to pop elements until a specific element is found.
78. Implement a function to interleave two stacks.
79. Write a function to find all possible subsets of a stack.
80. Implement a function to implement a stack with a fixed capacity.