Leetcode practice and solution (inspired by qiyuangong leetcode)

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No.	Title	Code	Basic idea	Level
990	Satisfiability of Equality Equations	Python	1. union-find 2. Create key and value 'a' to 'z'	Medium
989	Add to Array-Form of Integer	Python	Array convert to integer	Easy
988	Smallest String Starting From Leaf	Python	1. Using DFS and pop temp list until equal to level 2. Sort results and take the first one result	Medium
985	Sum of Even Numbers After Queries	Python	1. Calculate all even values of A 2. Subtract A[index] is even value and add value to A[index] and examine even values.	Easy
984	String Without AAA or BBB	Python	Decide A or B which is greater than the other, while(L-S >= 2 and L >= 2 and S >= 1), while(L > 0 and S > 0), add remaining 'a' or 'b'	Easy
257	Binary Tree Paths	Python	DFS, path_helper(cur, res, temp, level), pop()	Easy
146	LRU Cache	Python	Double Linked list, HashMap	Hard
129	Sum Root to Leaf Numbers	Python	DFS, calculate value each time	Medium
2	Add Two Numbers	Python	Linked List	Medium
1	Two Sum	Python	Hashmap	Easy