求二叉树深度

给定一棵二叉树的先序遍历序列和中序遍历序列，要求计算该二叉树的高度。

9 
ABDFGHIEC
FDHGIBEAC

示例输出

5

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#include <cmath>
#define inf 0x3f3f3f3f;
#define ls l,mid,rt<<1
#define rs mid+1,r,rt<<1|1
#define maxn 50000

char pre[maxn],mi[maxn];
using namespace std;
int n;
struct node
{
    char c;
    node *l,*r;
};
node *bu(char *pre,char *mi,int m)
{
   int k;
    if(m<=0)
    return NULL;
    node *head;
    head=new node ;
    head->c=*pre;
    char *p ;
    for(p=mi;p!=NULL;p++)
        if(*p==*pre)
            break;
    k=p-mi;
    head->l=bu(pre+1,mi,k);
    head->r=bu(pre+k+1,p+1,m-k-1);
    return head;
}

int deep(node *rt)
{
    int dl,dr;
    if(!rt)
    {
        return 0;
    }
    dl=deep(rt->l);
    dr=deep(rt->r);
    if(dl>dr)
        return dl+1;
    else
        return dr+1;
}

int main()
{
    int m,i,j,k;
    while(~scanf("%d",&n))
    {
        getchar();
        node *rt;
        rt=new node ;
        scanf("%s",pre);
        scanf("%s",mi);
        m=n;
        rt=bu(pre,mi,m);
        int p=deep(rt);
        cout<<p<<endl;
    }
    return 0;
}