0432. All O`one Data Structure

https://leetcode.com/problems/all-oone-data-structure

Description

Design a data structure to store the strings' count with the ability to return the strings with minimum and maximum counts.

Implement the AllOne class:

• AllOne() Initializes the object of the data structure.

• inc(String key) Increments the count of the string key by 1. If key does not exist in the data structure, insert it with count 1.

• dec(String key) Decrements the count of the string key by 1. If the count of key is 0 after the decrement, remove it from the data structure. It is guaranteed that key exists in the data structure before the decrement.

• getMaxKey() Returns one of the keys with the maximal count. If no element exists, return an empty string "".

• getMinKey() Returns one of the keys with the minimum count. If no element exists, return an empty string "".

Example 1:

**Input**
["AllOne", "inc", "inc", "getMaxKey", "getMinKey", "inc", "getMaxKey", "getMinKey"]
[[], ["hello"], ["hello"], [], [], ["leet"], [], []]
**Output**
[null, null, null, "hello", "hello", null, "hello", "leet"]
**Explanation**
AllOne allOne = new AllOne();
allOne.inc("hello");
allOne.inc("hello");
allOne.getMaxKey(); // return "hello"
allOne.getMinKey(); // return "hello"
allOne.inc("leet");
allOne.getMaxKey(); // return "hello"
allOne.getMinKey(); // return "leet"

Constraints:

• 1 <= key.length <= 10

• key consists of lowercase English letters.

• It is guaranteed that for each call to dec, key is existing in the data structure.

• At most 5 * 104 calls will be made to inc, dec, getMaxKey, and getMinKey.

ac