1813.cpp

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<string>
#include<cmath>


using namespace std;


struct Node
{
    Node *lchild;
    Node *rchild;
    char c;
} Tree[50];
int loc;
Node *creat()
{
    Tree[loc].lchild = Tree[loc].rchild = NULL;
    return &Tree[loc ++];
}
char str1[30] , str2[30];
void postOrder(Node *T)
{
    if (T -> lchild != NULL)
    {
        postOrder(T -> lchild);
    }
    if (T -> rchild != NULL)
    {
        postOrder(T -> rchild);
    }
    printf("%c",T -> c);
}
//由字符串的前序遍历和中序遍历还原树,
//并返回其根节点,其中前序遍历结果为
//由str1[s1]到str2[e1]，中序遍历结果为str2[s2]到str2[e2]
Node *build(int s1,int e1,int s2,int e2)
{


    Node* ret = creat();
    ret -> c = str1[s1];
    int rootIdx;
    for (int i = s2; i <= e2; i ++)
    {
        if (str2[i] == str1[s1])
        {
            rootIdx = i;
            break;
        }
    }
    if(rootIdx != s2)
    {
        ret->lchild=build(s1+1,s1+(rootIdx-s2),s2,rootIdx-1);
    }
    if(rootIdx != e2)
    {
        ret->rchild=build(s1+(rootIdx-s2)+1,e1,rootIdx+1,e2);
    }
    return ret;
}
int main ()
{
    while (scanf ("%s %s",str1,str2) != EOF)
    {
        loc = 0;
        int L1 = strlen(str1);
        int L2 = strlen(str2);
        Node *T = build(0,L1 - 1,0,L2 - 1);
        postOrder(T);//后序遍历
        printf("\n");
    }
    return 0;
}//Parsed in 0.123 seconds