The height of a rooted tree is the number of edges on the longest downward path between the root and a leaf. 这个题目思路来自于Solution, 类似于剥洋葱, 从leaves开始一层一层往里面剥, 依次更新leaves, 到最后只剩一个或2个nodes的时候(因为根据tree的定义, 从数学上可以证明最多只有两个root的heigh...