C语言之二叉树的遍历

typedef int BTDataType;
 
//二叉树节点的结构
typedef struct BTNode
{
	BTDataType data;
	struct BTNode* left;
	struct BTNode* right;
}BTNode;
 
//定义一个申请新节点的函数
BTNode* BuyBTNode(BTDataType data)
{
	BTNode* newNode = (BTNode*)malloc(sizeof(BTNode));
	if (newNode == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}
 
	newNode->data = data;
	newNode->left = NULL;
	newNode->right = NULL;
 
	return newNode;
 }
 
int main()
{
	//手动申请节点加连接
	BTNode* n1 = BuyBTNode(1);
	BTNode* n2 = BuyBTNode(2);
	BTNode* n3 = BuyBTNode(3);
	BTNode* n4 = BuyBTNode(4);
	BTNode* n5 = BuyBTNode(5);
	BTNode* n6 = BuyBTNode(6);
 
	n1->left = n2;
	n1->right = n4;
	n2->left = n3;
	n4->left = n5;
	n4->right = n6;
	return 0;
}

void PrevOrder (BTNode* root)

void PrevOrder(BTNode* root)
{
	if (root == NULL)
	{ 
		printf("NULL ");//空节点用 NULL 表示
		return; 
	}
 
	printf("%d ", root->data);//前序在前
	PrevOrder(root->left);
	PrevOrder(root->right);
}

int main()
{
	//手动申请节点加连接
	BTNode* n1 = BuyBTNode(1);
	BTNode* n2 = BuyBTNode(2);
	BTNode* n3 = BuyBTNode(3);
	BTNode* n4 = BuyBTNode(4);
	BTNode* n5 = BuyBTNode(5);
	BTNode* n6 = BuyBTNode(6);
 
	n1->left = n2;
	n1->right = n4;
	n2->left = n3;
	n4->left = n5;
	n4->right = n6;
 
	PrevOrder(n1);
	return 0;
}

void InOrder(BTNode* root)

void InOrder(BTNode* root)
{
	if (root == NULL)
	{
		printf("NULL ");
		return;
	}
 
	PrevOrder(root->left);
	printf("%d ", root->data);//中序在中
	PrevOrder(root->right);
}

void PostOrder(BTNode* root)
{
	if (root == NULL)
	{
		printf("NULL ");
		return;
	}
 
	PostOrder(root->left);
	PostOrder(root->right);
	printf("%d ", root->data);//后序在后
}