主要操作过程：

建立一般的二叉链表，通过遍历进行线化，设p为当前处理结点，pre为p的前驱填标志：

若p无左：p->ltag=1；若p无右：p—>rtag=1；填线索：若p->ltag==1: p->lchild=pre 若pre->rtag== pre->rchild=p

-The main process: the establishment of a general binary list, for through the traverse line, and set up to deal with p for the current node, pre filled for signs precursor p: p if not left: p->　ltag = 1　if the p-free Right: p->　rtag = 1　filling clue: If p->　ltag == 1: p->　lchild = pre　if the pre->　rtag == pre->　rchild = p