Tree Recovery poj2255(前序中序遍历建立二叉树)

题目链接：Tree Recovery poj2255

题意：
给出一个前序遍历序列和中序遍历序列，输出后序遍历序列

跟之前的给后序和中序遍历序列一样

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <sstream>

using namespace std;

typedef long long ll;

const int inf = 0x3f3f3f3f;
const int maxn = 30;

int l[maxn],r[maxn];

string fo_order,in_order;

void build(int l1,int r1,int l2,int r2)
{
    if(l1 > r1){
        return ;
    }
    char root = fo_order[l2];
    int k  = l1;
    while(in_order[k] != root){
        k++;
    }
    int cnt = k - l1;
    build(l1,k - 1,l2 + 1,l2 + cnt);
    build(k + 1,r1,l2 + cnt + 1,r2);
    cout<<root;
}


int main()
{
    while(cin>>fo_order>>in_order){
        int strl = fo_order.size();
        build(0,strl - 1,0,strl - 1);
        cout<<endl;
    }
    return 0;
}