Add an extension problem of create a balanced BST from a linkedlist:
C5_11A_SortedList2BalancedBST, the solution is based on in-order
traverse.
Add following question from LeetCode
1. generate unique BST using 1-n, it's a Catalan seq, C5_27_UniqueBST
2. JumpGame C1_80_JumpGame
3. refine the code of C3_10_ListPartition
4. get letter combination based on a phone number, C1_81_LetterCombinationOfPhoneNumber
5. add a application question of gas station: C1_82_GasStation