Confluent

Given a string array where each string represents employee chair events:

Characters represent actions:

• 'C': New employee joins, needs a chair
• 'U': Employee goes to meeting room (frees chair)
• 'L': Employee returns from meeting (needs chair)
• 'R': Employee leaves company (frees chair)

Task: Calculate minimum chairs needed to purchase.

Example: Input: ["C", "U", "L", "R"] Output: 1

Rules:

• Start with 0 chairs
• Must buy new chair if no spare chairs available
• Track available chairs as employees move
• Return array of minimum chairs needed for each string

Note: Need to buy chair immediately when needed (can't wait for future events).

Calculate minimum initial health needed to defeat opponents in a game.

Requirements:

• Start with n opponents at first level
• initial_players[i] represents opponent strength
• next_players list shows new players added each level
• Must defeat player at position 'rank' each level
• Health decreases by defeated opponent's strength
• Must keep health >= 0 throughout game

Example:

initial_players = [3, 2, 4]
next_players = [[1, 5], [2]]
rank = 2

Solution approach:
- Maintain min heap of size 'rank'
- Track health changes after each battle
- Consider new players added each level

Implement a Sudoku validator and solver.

Part 1: Validation

• Check if current board state is valid
• Verify rows, columns, and 3x3 boxes
• Handle partially filled boards

Part 2: Solver

• Implement backtracking solution
• Fill empty cells (represented by '.')
• Ensure all solutions are valid

Follow-up:

• Optimize solution for large boards
• Handle multiple valid solutions
• Implement visualization of solving process

Implement a wildcard pattern matching function.

Requirements:

• Match literal characters (a-z)
• Support '*' wildcard (matches 0 or more of any char)
• Initially focus on 0-1 wildcards
• Later handle multiple wildcards

Examples:

pattern: "a*b", string: "acb" → true
pattern: "a*", string: "abc" → true
pattern: "a*c", string: "ab" → false

Follow-up:

• Handle multiple wildcards efficiently
• Optimize for long strings
• Consider memory usage