》》如何用C语言构建一颗二叉树？ 

第一种方法：

ThreadTree A = (ThreadTree)malloc(sizeof(ThreadNode));
	A->data = { 'A' };
	A->ltag = 0;
	A->rtag = 0;
	A->lchild = NULL;
	A->rchild = NULL;

	ThreadTree B = (ThreadTree)malloc(sizeof(ThreadNode));
	B->data = { 'B' };
	A->lchild = B;
	B->ltag = 0;
	B->rtag = 0;
	B->lchild = NULL;
	B->rchild = NULL;

	ThreadTree C = (ThreadTree)malloc(sizeof(ThreadNode));
	C->data = { 'C' };
	A->rchild = C;
	C->lchild = NULL;
	C->rchild = NULL;
	C->ltag = 0;
	C->rtag = 0;