已知二叉树的中序遍历序列和后序遍历序列，求前序遍历序列

#include <bits/stdc++.h>
using namespace std;

char* in = (char *)malloc(sizeof(char));
char* post = (char *)malloc(sizeof(char));

struct node
{
    char data;
    node *left, *right;
};

node *create(int postL, int postR, int inL, int inR)
{
    if (postL > postR)
        return NULL;
    node *root = new node;
    root->data = post[postR];
    int k;
    for (k = inL; k < inR; k++)
        if (in[k] == post[postR])
            break;
    int num = k - inL;
    root->left = create(postL, postL + num - 1, inL, k - 1);
    root->right = create(postL + num, postR - 1, k + 1, inR);
    return root;
}

void preOrder(node *root)
{
    if (root == NULL)
        return;
    cout << root->data;
    preOrder(root->left);
    preOrder(root->right);
}

int main()
{
    scanf("%s", in);
    scanf("%s", post);
    int len = strlen(in);
    node *root = create(0, len - 1, 0, len - 1);
    preOrder(root);
    return 0;
}