Python Developer

Start by iterating through the list. For each number, calculate its complement by subtracting the current number from the target value. Check if this complement is already in the set of seen numbers. If it is, you’ve found a valid pair, so add it to the pairs set, ensuring the smaller number comes first.

After checking, add the current number to the set of seen numbers to use it in future comparisons. Once you’ve processed all numbers, convert the set of pairs to a list and return it. This approach ensures efficiency and correctness.

To solve the problem of determining if a word can be formed by sequentially adjacent cells on a 2D board, use Depth-First Search (DFS) with backtracking. Start DFS from each cell, checking if the current cell matches the corresponding character in the word. If it does, recursively explore neighbouring cells while marking the current cell as visited to avoid reuse. If the entire word is matched, return True; otherwise, backtrack by unmarking the cell and continue searching. If any DFS from a starting cell successfully matches the word, return True; otherwise, return False after checking all cells.