前序 + 中序

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

deque<int> rear,center,pref;

void build(deque<int> pre,deque<int> cen){
    int temp;
    if(pre.size()) temp = pre.front();
    else return;

    int pos;
    for(int i = 0;i < cen.size();i ++){
        if(cen[i] == pre.front()){
            pos = i;
            break;
        }
    }

    pre.pop_front();

    deque<int> p,c;
    p.assign(pre.begin(),pre.begin() + pos);
    c.assign(cen.begin(),cen.begin() + pos);
    build(p,c);

    p.clear(),c.clear();
    p.assign(pre.begin() + pos,pre.end());
    c.assign(cen.begin() + pos + 1,cen.end());
    build(p,c);

    rear.push_back(temp);
}

int main(){
    int n;
    cin >> n;

    for(int i = 0;i < n * 2;i ++){
        int t;
        cin >> t;

        if(i < n) center.push_back(t);
        else pref.push_back(t);
    }

    build(pref,center);

    for(auto i : rear) cout << i << ' ';
}

中序 + 后序

#include<iostream>
#include<vector>

using namespace std;

const int N = 50;

vector<int> rear;
vector<int> center;
vector<int> pre;

int n;

void build(vector<int> re,vector<int> cen){
    if(re.size()) pre.push_back(re.back());
    else return;

    int pos;
    for(int i = 0;i < cen.size();i ++){
        if(cen[i] == re.back()){
            pos = i;
            break;
        }
    }
    
    re.pop_back();

    vector<int> r,c;
    r.assign(re.begin(),re.begin() + pos);
    c.assign(cen.begin(),cen.begin() + pos);
    build(r,c);

    r.clear(),c.clear();
    r.assign(re.begin() + pos,re.end());
    c.assign(cen.begin() + pos + 1,cen.end());
    build(r,c);
}

int main(){
    cin >> n;

    for(int i = 0;i < n * 2;i ++){
        int t;
        cin >> t;

        if(i < n) rear.push_back(t);
        else center.push_back(t);
    }

    build(rear,center);

    cout << "Preorder:";
    for(auto i : pre) cout << ' ' << i;
}

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