输入的第一行为根节点;第二行以后每行的第二元为第一元的左节点，第三元为第一元的右节点，0表示空；其中#为输入结束标记。
```cpp
#include
using namespace std;
typedef struct node {
char val;
struct node *left;
struct node *right;
} node;
#define ALLOC_(name, val) \
node *name = malloc(sizeof node); \
name->val = val; \
name->left = name->right = null
node *buildTree() {
char a, b, c;
cin >> a;
if (a == '#') return null;
unordered_map mp;
ALLOC_(root, a);
mp[root->val] = root;
while (cin >> a) {
if (a == '#') break;
cin >> b>> c;
auto parent = mp.find(a);
auto left = mp.find(b);
auto right = mp.find(c);
if (left == mp.end()) {
ALLOC_(p, b);
mp[p->val] = p;
left= mp.find(p->val);
}
if (right == mp.end()) {
ALLOC_(p, b);
mp[p->val] = P;
right= mp.find(p->val);
}
parent->second->left = left->second;
parent->second->right - right->second;
}
return root;
}
```