1. Word Search in Grid 
Given an m x n grid of characters board and a string word, return true if word exists in the grid.
The word can be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once.
Example 1:
Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCCED" Output: true
Example 2:
Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "SEE" Output: true
Example 3:
Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCB" Output: false
Constraints:
- m == board.length
- n = board[i].length
- 1 <= m, n <= 6
- 1 <= word.length <= 15
- board and word consists of only lowercase and uppercase English letters.
Follow up: Could you use search pruning to make your solution faster with a larger board?
2. Design an E-commerce System
Design an e-commerce system. Start with simple requirements and discuss how to scale the system. Consider aspects such as user experience, performance, and scalability. Discuss your approach and any considerations you would take into account.
3. Warehouse Operations: FIFO Queue for Ship Order
Implement a FIFO queue for the 'Ship_order' operation in the warehouse system. Describe how you would modify the existing 'Ship_order' method to adhere to FIFO principles.
4. Warehouse Operations: FIFO Queue for Add Product
Implement a FIFO queue for the 'Add_product' operation in the warehouse system. Describe how you would modify the existing 'Add_product' method to adhere to FIFO principles.
5. Warehouse Operations: Return Order
Implement a method 'Return_order' that takes a list of id numbers as input and determines if all the products can be returned to the warehouse. The method should return true if all products can be returned, otherwise false.
