用一个结构体存储每个节点，每个结构体包括一个char 和指向左右孩子的指针，每次扫进来它自身的char和i， 如果i为偶则放进左子树，否则放进右子树。然后就是利用递归前序遍历此树-Structure with a store on each node, each structure includes a char and a pointer to the children about each sweep into its own char and i, for even if i was into the left subtree, or else into the right sub-树. Then there is the use of recursive traversal of this tree before