已知前序和中序,求后序遍历

时间:2021-06-08 12:38:48

通过简单例子可以分析出,先由前序找出当前根,再通过中序找出左右子树序列,然后递归输出左右子树,最后输出根


#include "stdafx.h"
#include <iostream>
using namespace std;

void GetEnOrder(char* startPreOrder,char* endPreOrder,char* startInOrder,char* endInOrder);

void GetAll(char* preOrder,char* inOrder,int lenght)
{
	if (preOrder==NULL||inOrder==NULL||lenght<=0)
	{
		return;
	}

	GetEnOrder(preOrder,preOrder+lenght-1,inOrder,inOrder+lenght-1);
}

void GetEnOrder(char* startPreOrder,char* endPreOrder,char* startInOrder,char* endInOrder)
{
	if (startPreOrder<=endPreOrder)
	{
		char root=*startPreOrder;
	
		char* rootInOrder=startInOrder;
		while(rootInOrder<=endInOrder&&*rootInOrder!=root)
		{
			rootInOrder++;
		}
		if (rootInOrder==endInOrder+1)
		{
			throw std::exception("序列错误!");
		}
	
		int leftLen=rootInOrder-startInOrder;
		int rightLen=endInOrder-rootInOrder;
	
		if (leftLen>0)
		{
			GetEnOrder(startPreOrder+1,startPreOrder+leftLen,startInOrder,rootInOrder-1);
		}
		if(rightLen>0)
		{
			GetEnOrder(startPreOrder+leftLen+1,endPreOrder,rootInOrder+1,endInOrder);
		}
		cout<<root;
	}		
}


int _tmain(int argc, _TCHAR* argv[])
{
	char preOrder[]={'A','B','D','C'};
	char inOrder[]={'B','D','A','C'};
	GetAll(preOrder,inOrder,4);

	return 0;
}