设有一棵满二叉树（所有结点值均不同），已知其先序序列为pre，设计一个算法求其后序序列post

#include <iostream>
#include <stack>
#include <queue>
#include<string.h>
typedef struct treenode{
    char data;
    struct treenode *left;
    struct treenode *right;
}treenode,*ptreenode;

ptreenode buytreenode(char x)
{
    ptreenode n=(ptreenode) malloc(sizeof (treenode));
    n->data=x;
    n->left= nullptr,n->right= nullptr;
    return n;
}
ptreenode build_tree()
{
    ptreenode root= buytreenode('A');
    root->left= buytreenode('B');
    root->right= buytreenode('C');
    root->left->left= buytreenode('D');
    root->left->right= buytreenode('E');
    root->right->left= buytreenode('F');
    root->right->right= buytreenode('G');
    root->left->left->left= buytreenode('H');
    root->left->left->right= buytreenode('I');
    return root;
}

ptreenode build_tree2()
{
    ptreenode root= buytreenode('A');
    root->left= buytreenode('B');
    root->right= buytreenode('C');
    root->left->left= buytreenode('D');
    root->left->right= buytreenode('E');
    root->right->left= buytreenode('F');
    root->right->right= buytreenode('G');
    root->left->left->left= buytreenode('H');
    root->left->left->right= buytreenode('I');
    root->left->right->left= buytreenode('J');
    root->left->right->right= buytreenode('K');
    root->right->left->left= buytreenode('L');
    root->right->left->right= buytreenode('M');
    root->right->right->left= buytreenode('N');
    root->right->right->right= buytreenode('O');
    return root;
}

void print_tree(ptreenode root) {
    std::queue<ptreenode> tmp;
    tmp.push(root);
    int s = tmp.size();
    while (!tmp.empty()) {
        ptreenode t = tmp.front();
        tmp.pop();
        s--;
        printf("%3c", t->data);
        if (t->left) tmp.push(t->left);
        if (t->right) tmp.push(t->right);
        if (s == 0) puts(""), s = tmp.size();
    }
}

void print_pre(ptreenode root)
{
    if(root== nullptr) return;
    printf("%3c",root->data);
    print_pre(root->left);
    print_pre(root->right);
}

void print_post(ptreenode root)
{
    if(root== nullptr) return;;
    print_post(root->left);
    print_post(root->right);
    printf("%3c",root->data);
}

void pre2post(char *pre,int l1,int h1,char* &post,int l2,int h2)
{
    int half;
    if(h1>=l1){
        post[h2]=pre[l1];
        half=(h1-l1)/2;
        pre2post(pre,l1+1,l1+half,post,l2,l2+half-1);
        pre2post(pre,l1+half+1,h1,post,l2+half,h2-1);
    }
}
void pretopost(char* record,int size)
{
    char *post=(char*) malloc(sizeof (char)*(size+1));
    memset(post,0,sizeof (char)*(size+1));
    pre2post(record,0,size,post,0,size);
    printf("our post order: ");
    for(int i=0;i<=size;i++) printf("%3c",post[i]);
}
int main() {
    ptreenode root=build_tree2();
    print_tree(root);

    puts("");
    printf("the pre order: ");
    print_pre(root);
    puts("");
    printf("the post order: ");
    print_post(root);
    puts("");

    char pre_record[]={"ABDHIEJKCFLMGNO"};
    pretopost(pre_record,14);
    return 0;
}