Array vs Map Children

Two common ways to store children in a trie node: Array (fixed alphabet):

children: array of 26 (for lowercase letters)
# Access: children[ord(c) - ord('a')]

Hash map (flexible):

children: map from char to TrieNode
# Access: children.get(c)

Trade-offs:

• Array: $O(1)$ access, wastes space for sparse tries
• Map: Slight overhead, memory-efficient for large alphabets

For lowercase English letters, array is typically faster.

For Unicode or variable alphabets, map is necessary. Choose based on your alphabet size and sparsity. Time: $O(L)$. Space: $O(L)$.