Trie

Building a Trie from nested dicts, counting on nodes, pairing it with DFS, and when a Trie is not actually needed

LeetCode 212 note: build a Trie of all words, walk it during the grid DFS, remove words once found, and prune empty nodes

LeetCode 2416 note: each Trie node counts the words passing through it, and a word’s answer is the sum of counts along its path

LeetCode 1178 note: a word only matters by its set of letters, so count 26-bit masks and enumerate each puzzle’s submasks

LeetCode 1023 note: two pointers character by character; anything beyond the pattern must be lowercase

LeetCode 2781 note: forbidden words are at most 10 long, so each right end checks only the last 10 suffixes; on a match push the left end past it, using the shortest match (the rightmost start)

LeetCode 208 note: each node is a children dict plus an is_end flag; insert, search and startsWith all walk down character by character

LeetCode 14 note: bound by the shortest string and check each position across all strings; the first mismatch gives the answer’s length