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: //如果有子节点，字符串随着递归一直累加，直到没 阅读全文

摘要：Invert a binary tree. to Trivia:This problem was inspired by this original tweet by Max Howell: 方法一：递归 方法二：非递归，栈 阅读全文

摘要：Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest l 阅读全文

摘要：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet 阅读全文

摘要：39、combination sum1 Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the can 阅读全文