已知中序、後序 序列重構二叉樹

#include<cstdio>
#include<string>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=200020;
struct Tree{
    string str;
    char x;
    Tree *l,*r;
    Tree():l(NULL),r(NULL){};
};
string s,t;
void dfs(Tree* node,string in,string after);
void print(Tree* node);
int main()
{
    //freopen("in.txt","r",stdin);
    Tree* T=new Tree;
    cin>>s>>t;
    dfs(T,s,t);
    print(T);
    return 0;
}
void dfs(Tree* node,string in,string after){
        char c=after[after.size()-1];
        node->x=c;
        //printf("%c",node->x);
        int k=in.find(c);
        //substr():第一個參數爲字符串開始位置，第二個參數爲長度
        if(k!=0){//建左子樹
            node->l=new Tree;
            dfs(node->l,in.substr(0,k),after.substr(0,k));
        }
        if(after.size()-k-1!=0){//建右子樹
            node->r=new Tree;
            dfs(node->r,in.substr(k+1),after.substr(k,after.size()-k-1));
        }
}
void print(Tree* node){//先序遍歷
    //cout<<"1";
    cout<<node->x;
    if(node->l!=NULL)
        print(node->l);
    if(node->r!=NULL)
        print(node->r);
}

相關題目：洛谷P1030https://www.luogu.org/problem/show?pid=1030