String

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 940 note: group by last character; distinct subsequences ending with c = every current distinct subsequence with c appended, plus c itself, replacing the old value

LeetCode 1028 note: a stack holds the path from the root to the current node, so its length is the depth

LeetCode 301 note: compute the minimum left and right deletions before backtracking, or BFS one deletion per level and stop at the first valid level

LeetCode 420 note: three length cases; when too long, delete from runs with len % 3 == 0 first to cancel replacements

LeetCode 2193 note: greedily fix the outer pair: take the last character and swap its leftmost partner to the front, costing that index; the unpaired character ends in the middle, costing its distance there

LeetCode 4026 note: greedily match from the left for each worker’s earliest station and from the right for the latest; splitting between workers i and i+1, the largest gap is latest[i+1] - earliest[i]

LeetCode 1320 note: after typing word[i], one finger is always on word[i], so the state is only the other finger’s position; dp[other] is the least distance with the other finger at other

LeetCode 902 note: digit DP with state (pos, tight, started); before starting, a position can be skipped, representing numbers with fewer digits than n

LeetCode note for Shortest Common Supersequence, rebuilt from the original learning note

LeetCode note for Minimum ASCII Delete Sum for Two Strings, rebuilt from the original learning note

LeetCode note for Minimum Insertion Steps to Make a String Palindrome, rebuilt from the original learning note