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为其父结点，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 top-down by the level of input from left to right each node of a triple (N, P, L/R). One N-based node elements, P node for his father, L instructions N to P s left child, R instructions N to P s right child. Written test to establish a binary tree in memory of the double-stranded said algorithm, and the achievement of the first root, root, root, as well as sequence traversal algorithm.