摘要：
Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: All root-to-leaf paths are: Credits:Special thanks t 阅读全文
摘要：
Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be 阅读全文
摘要：
Remove all elements from a linked list of integers that have value val. ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 -- 阅读全文