Hash-Table

LeetCode 748 note: count the plate’s letters in lowercase, then find the shortest word covering every count, taking the earliest on ties

LeetCode 705 note: a fixed number of buckets, with the key modulo the bucket count choosing the bucket and a list per bucket handling collisions

LeetCode 697 note: record each value’s count, first index and last index; among the most frequent values, take the shortest span

LeetCode 653 note: traverse while keeping a set of seen values; finding k - val in it means a pair exists

LeetCode 645 note: use sums: missing = sum of 1..n - sum of the set, duplicate = array sum - sum of the set

LeetCode 599 note: map list1’s strings to indices, sum both indices while scanning list2, and keep every string with the minimum sum

LeetCode 594 note: subsequences need not be contiguous, so just count; for each x add the counts of x and x + 1

LeetCode 575 note: at most n / 2 candies can be eaten and at most len(set) kinds exist; the answer is the smaller of the two

LeetCode 500 note: make a set for each keyboard row and keep words whose lowercase character set is a subset of one row

LeetCode 448 note: use the array itself as the hash table, marking nums[x - 1] negative for each x; positions still positive are the missing numbers

LeetCode 409 note: use an even number of each character on the two sides, plus one in the middle if any count is odd

LeetCode 389 note: t has one extra character; XOR every character of both strings, pairs cancel, and the extra one remains