二叉树遍历

#include <iostream>
#include <string>
using namespace std;
struct node
{
    char val;
    node *left, *right;
    node(char x) : val(x), left(NULL), right(NULL) {}
};
string pre, in;
node* Create(int preL, int preR, int inL, int inR){
    if(preL > preR){
        return NULL;
    }
    node* root = new node(pre[preL]);
    int k;
    for(k = inL; k <= inR; k++){
        if(in[k] == pre[preL]){
            break;
        }
    }
    int numLeft = k - inL;
    root->left = Create(preL + 1, preL + numLeft, inL, k - 1);
    root->right = Create(preL + numLeft + 1, preR, k + 1, inR);
    return root;
}
void postOrder(node* root){
    if(root == NULL){
        return;
    }
    postOrder(root->left);
    postOrder(root->right);
    cout << root->val;
}
int main()
{
    while(cin >> pre >> in){
        node* root = Create(0, pre.length() - 1, 0, in.length() - 1);
        postOrder(root);
        cout << endl;
    }
    return 0;
}