假设自上而下按层次，自左至右输入每个结点的一个三元组(N, P, L/R)。其中N为本结点的元素，P为其夫结点，L指示N为P 的左孩子，R指示N为P的右孩子。试写一个建立二元树在内存的双链表示算法，并实现先根、中根、后根以及层序遍历算法。

-Assuming that the top-down hierarchy, from left to right input each node is a triple (N, P, L/R). N oriented junction element the P their husband junction point, L indicator N is the left child of P, R indicator N is the right child of P. Try to write an algorithm build a binary tree in memory double-stranded and first root, root, dorsal root sequence traversal algorithm.