1086. Tree Traversals Again (25)

#include<iostream> 
#include <sstream>   //将string转化成int 
#include<string>     //定义string类型字符串 
#include<stack>  
#define MAXSIZE 100
using namespace std;  

typedef int ElemType;
struct BTNode{
	ElemType data;
	BTNode * lchild;
	BTNode * rchild;
};

//先序+中序=建树   
BTNode *  PreInCreate(ElemType pre[],ElemType in[],int len){  
    if(pre==NULL || in==NULL || len<=0) return NULL;  
    int i=0;  
    BTNode * T=new BTNode;  
    T->lchild=T->rchild=NULL;  
    int leftlen,rightlen;  
    ElemType tmp=pre[0];  
      
    T->data=tmp;  
      
    while(i<len){  
        if(in[i]!=tmp) i++;  
        else   break;         
    }  
      
    leftlen=i;rightlen=len-i-1;  
    if(leftlen>0) T->lchild=PreInCreate(pre+1,in,leftlen);  
    if(rightlen>0) T->rchild=PreInCreate(pre+leftlen+1,in+leftlen+1,rightlen);  
    return T;  
}  

//后序遍历    
void PostOrder(BTNode * T,bool flag){    //flag=true表示可以输出空格 
    //这步判断一定要有，处理建树时的return NULL     
    if(T){    
        PostOrder(T->lchild,true);    
        PostOrder(T->rchild,true);    
        cout<<T->data;   
		if(!flag) flag=true;
		else   cout<<" ";   
    }     
}  
  
int  main(){  
	//freopen("input.txt","r",stdin);
	int n;    
	stringstream ss;  
	string Nstr;  
    getline(cin,Nstr);  
    ss << Nstr; ss >> n; ss.clear();  //cout<<n;  
    
    
	stack<int> myStack;
	int pre[MAXSIZE],in[MAXSIZE];
	string key; int data;

	int preidx=0,inidx=0;
	
	
	for(int i=0;i<2*n;i++){
		getline(cin,key);
		//cout<<key[1]<<"hahaha";return 0;
		if(key[1]=='u'){ //"u"表示字符串，'u'表示一个字符 
			string datastr=key.substr(5);
			ss<<datastr; ss>>data; ss.clear();
			pre[preidx++]=data;
			myStack.push(data); 
		}else{
			int tmp=myStack.top();
			in[inidx++]=tmp;
			myStack.pop();			
		}		
	}

	BTNode * T;
	T=PreInCreate(pre,in,preidx); //因为最后一步多+1 
	PostOrder(T,false); 

	return 0;  
}