6-3 二叉树的重建 uva536

已知先序和中序  求后序

可以有两种方式输出

一种是建好树按照树输出

一种是不建树  在遍历的过程中存入vector  再倒叙输出

#include<bits/stdc++.h>
using namespace std;

int ri[];int le[];
char xian[],zhong[];vector<char>ans;

int built(int x1,int y1,int x2,int y2)
{
    if(x2>y2||x1>y1)return ;

    char root=xian[x1];
     ans.push_back(root);
    int p=x2;
    while(zhong[p]!=root)p++;
    int cnt=p-x2;

     ri[root]=built(x1+cnt+,y1,x2+cnt+,y2);
     le[root]=built(x1+,x1+cnt,x2,x2+cnt-);
    return root;

}

void dfs(int root)
{

    if(le[root]){dfs(le[root]);}
    if(ri[root]){dfs(ri[root]);}
    printf("%c",root);
    return;
}

int main()
{

    while(scanf("%s %s",xian+,zhong+)==)
    {  ans.clear();

        int n=strlen(xian+);

       int root=built(,n,,n);

       //for(int i=ans.size()-1;i>=0;i--)
      //  cout<<ans[i];
      dfs(root);
       cout<<endl;

    }

    return ;
}