41. Write a program to find the longest common subsequence of three strings.
42. Write a program to implement a basic token-based authentication system.
43. Write a program to solve the problem of finding the kth smallest element in a stream.
44. Write a program to implement a simple web crawler.
45. Write a program to perform a binary search on a rotated sorted array.
46. Write a program to find the maximum sum of non-adjacent elements in an array.
47. Write a program to implement a task scheduler.
48. Write a program to check if a string can be segmented into words from a dictionary.
49. Write a program to find the shortest palindrome that can be formed from a string.
50. Write a program to implement a basic event-driven simulation.
51. Write a program to solve the job scheduling problem with deadlines.
52. Write a program to implement the Floyd-Warshall algorithm for finding shortest paths.
53. Write a program to solve the longest common prefix problem.
54. Write a program to implement a text editor with undo and redo functionality.
55. Write a program to find the longest substring with at most k distinct characters.
56. Write a program to find the number of ways to tile a 2xN board with 1x2 tiles.
57. Write a program to implement a simple web service using RESTful principles.
58. Write a program to find the maximum product of two integers in an array.
59. Write a program to solve the problem of valid Sudoku.
60. Write a program to implement a priority queue using a binary heap.
61. Write a program to implement a basic spam filter using Naive Bayes.
62. Write a program to perform heap sort on an array.
63. Write a program to find the longest path in a matrix with obstacles.
64. Write a program to implement a Sudoku solver.
65. Write a program to find the longest palindromic subsequence in a string.
66. Write a program to implement the binary indexed tree (Fenwick tree).
67. Write a program to implement a simple online file storage system.
68. Write a program to implement a spell checker using a dictionary.
69. Write a program to solve the 8-queens problem using backtracking.
70. Write a program to implement the Boyer-Moore algorithm for string searching.
71. Write a program to calculate the number of connected components in a graph.
72. Write a program to implement a basic online payment system.
73. Write a program to solve the problem of finding the first unique character in a string.
74. Write a program to find the number of islands in a 2D grid using DFS.
75. Write a program to implement a simple online calendar application.
76. Write a program to solve the problem of finding a peak element in an array.
77. Write a program to implement a simple object-oriented game engine.
78. Write a program to solve the problem of generating all combinations of a set.
79. Write a program to find the largest square of 1s in a binary matrix.
80. Write a program to implement the Dijkstra algorithm for finding the shortest paths.