【数据结构】树的遍历，等价中级表达式

#include <iostream>
#include <string>
using namespace std;

string str;
int i;
int j=0;
int cnt = 0;
struct TreeNode
{
    char value;
    struct TreeNode* lchild, * rchild;
    TreeNode(char c) : value(c), lchild(NULL), rchild(NULL) {}
};
TreeNode* creatTree()
{
    char c = str[i++];
    if (c == '#') return NULL;
    TreeNode* root = new TreeNode(c);
    root->lchild = creatTree();
    root->rchild = creatTree();
    return root;
}
void inorder(TreeNode* root)
{
    if (!root)
    {
        return;
    }
    if(root->lchild==NULL&&root->rchild==NULL)
        cout << root->value;
    else
    {
        if (cnt != 0)
        {
            cout << "(";
        }
        cnt++;
        inorder(root->lchild);
        cout << root->value;
        inorder(root->rchild);
        if (cnt-1 != j)
        {
            cout << ")";
            j++;
        }
    }
    
}

int main()
{
    cin >> str;
    i = 0;
    TreeNode* root = creatTree();
    inorder(root);
    cout << endl;
    return 0;
}