All O(1) Data Structure · Coding Interview Practice

All O(1) Data StructureDesign a structure that stores string counts with inc(key), dec(key), getMaxKey() and getMinKey(), each in O(1) time. inc adds the key with count 1 if absent; dec removes it when its count reaches 0. getMaxKey and getMinKey return any key with the highest or lowest count, or "" if empty.Constraints

1 <= key.length <= 10

key consists of lowercase English letters

At most 5 * 10^4 calls; dec is only called for existing keys

Examples

Input: inc("hello"), inc("hello"), getMaxKey(), getMinKey(), inc("leet"), getMaxKey(), getMinKey() Output: ["hello", "hello", "hello", "leet"]

Input: inc("a"), dec("a"), getMaxKey() Output: [""]

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