题解 | #二叉树遍历#

#include <stdio.h>
#include<assert.h>
#include<stdlib.h>
typedef char BTDataType;

typedef struct BinaryTreeNode
{
	BTDataType _data;
	struct BinaryTreeNode* _left;
	struct BinaryTreeNode* _right;
}BTNode;
BTNode* BuyNewBTNode(BTDataType x)
{
	BTNode* newnode = (BTNode*)malloc(sizeof(BTNode));
	if (newnode == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}
	newnode->_data = x;
	newnode->_left = NULL;
	newnode->_right = NULL;
	return newnode;
}
// 通过前序遍历的数组"ABD##E#H##CF##G##"构建二叉树
BTNode* BinaryTreeCreate(BTDataType* a,  int* pi)
{
	assert(a);
	if (a[*pi] == '#' || a[*pi] == '\0')
	{
		(*pi)++;//步进
		return NULL;
	}

	BTNode* root = BuyNewBTNode(a[*pi]);
	(*pi)++;//步进

	root->_left = BinaryTreeCreate(a ,pi);
	root->_right = BinaryTreeCreate(a , pi);
	return root;
}
void BinaryTreeInOrder(BTNode* root)
{
	if (root == NULL)
	{
		return;
	}
	BinaryTreeInOrder(root->_left);
	printf("%c ", root->_data);
	BinaryTreeInOrder(root->_right);
}
int main() {
    char a[100];

    while (scanf("%s", a) != EOF) { // 注意 while 处理多个 case
        // 64 位输出请用 printf("%lld") to 
    int i = 0;
	BTNode*  root= BinaryTreeCreate(a,&i);
    BinaryTreeInOrder(root);
    }
    return 0;
}