//給定一棵二叉樹的前序遍歷和中序遍歷,求其後序遍歷
#include <iostream>
#include <string.h>
using namespace std;
typedef struct BinTree
{
char data;
BinTree* lchild;
BinTree* rchild;
} BinTree;
void RebuildTree(BinTree* &Tree,char *pre,char *in,int len)
{
Tree = new BinTree;
if(Tree!=NULL)
{
if(len<=0)//遞歸截止條件
{
Tree = NULL;
return ;
}
int index = 0;
while(index<len&&*(pre)!=*(in+index))
{
//尋找當前的root結點(包含子樹)
index++;
}
Tree->data = *(pre);
RebuildTree(Tree->lchild,pre+1,in,index);//去掉root結點
RebuildTree(Tree->rchild,pre+1+index,in+1+index,len-(index+1));//去掉左邊和根節點
}
return ;
}
void PostOrderTravese(BinTree* Tree)
{
//後序遍歷輸出
if(Tree==NULL)
return;
PostOrderTravese(Tree->lchild);
PostOrderTravese(Tree->rchild);
cout<<Tree->data<<" ";
}
int main()
{
char pre[101]; //string pre;
char in[101]; //string in;
cout<<"Inuput DLR and LDR:"<<endl;
while(cin>>pre>>in)
{
BinTree* tree;
int length = strlen(pre);
RebuildTree(tree,pre,in,length);
PostOrderTravese(tree);
cout<<endl;
}
return 0;
}
//給定一棵二叉樹的中序序遍歷和後序遍歷,求其後序遍歷
#include<iostream>
using namespace std;
typedef struct _btn{
int data;
struct _btn *lchild;
struct _btn *rchild;
}btn;
#define MAXN 65536
int inOrder [MAXN];
int postOrder [MAXN];
btn *buildtree(int io1,int io2,int po1,int po2)//中序的首尾元素座標,後序的首尾元素座標
{
int iolen=io2-io1+1;//中序的長度
int i;
btn *root=new btn;//新建的一個結點作爲根結點
root->data=postOrder[po2];//後序的最後一個元素是根結點
root->lchild=NULL;
root->rchild=NULL;//左右孩子初始化爲空
//在中序裏尋找根結點
for(i=0;i<iolen;++i)
{
if(root->data==inOrder[io1+i])
break;
}
//於是左子樹的中序從io1到io1+i-1,後序從po1到po1+i-1
//注意遞歸出口,只有當io1<=io1+i-1即i>=1時纔有意義
if(i>=1)
root->lchild=buildtree(io1,io1+i-1,po1,po1+i-1);
//右子樹類似
if(io1+i+1<=io2)
root->rchild=buildtree(io1+i+1,io2,po1+i,po2-1);
//返回根結點
return root;
}
void preOrder(btn *root)
{
if(root!=NULL)
{
cout<<root->data<<" ";
preOrder(root->lchild);
preOrder(root->rchild);
}
}
//後序遍歷,用於釋放二叉樹
void deletetree(btn *root)
{
if(root!=NULL)
{
deletetree(root->lchild);
deletetree(root->rchild);
delete root;
root=NULL;
}
}
int main()
{
int i=0;
while(cin>>inOrder[i++])
{
if(cin.get()!=' ')
break;
}
i=0;
while(cin>>postOrder[i++])
{
if(cin.get()!=' ')
break;
}
btn *root=buildtree(0,i-1,0,i-1);
preOrder(root);
deletetree(root);
return 0;
}