二叉树的构建

最新推荐文章于 2022-01-02 21:41:33 发布

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最新推荐文章于 2022-01-02 21:41:33 发布

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分类专栏：数据结构文章标签：先序创建二叉树前中序创建二叉树中后序创建二叉树

本文链接：https://blog.youkuaiyun.com/YL970302/article/details/86585290

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本文介绍了三种构建二叉树的方法：1.基于先序遍历的结果创建；2.结合先序和中序遍历创建；3.使用中后序遍历创建。详细探讨了每种方法的步骤和思路。

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一、利用先序遍历的结果创建

1：

void CreateTree4(BtNode *&ptr,ElemType *&str)
{
	if(NULL == str || *str == '#')
	{
		ptr = NULL;
	}
	else
	{
		ptr = Buynode();
		ptr->data = *str;
		CreateTree4(ptr->leftchild,++str);
		CreateTree4(ptr->rightchild,++str);
	}
}

int main()
{
    char *str="ABC##DE##F##G#H##";
    BtNode *root = NULL;
    CreateTree4(root,str);

    return 0;
}

2：

BtNode * CreateTree1()
{
	BtNode *s = NULL;
	ElemType item;
	cin>>item;
	if(item != '#')
	{
		s = Buynode();
		s->data = item;
		s->leftchild = CreateTree1();
		s->rightchild = CreateTree1();
	}
	return s;
}
int main()
{
	BtNode *root = NULL;
	root = CreateTree1();
        return 0；
}

二、利用先序、中序遍历的结果创建二叉树：

int  FindPos(ElemType *is,ElemType x,int n)
{
	int pos = -1;
	for(int i = 0;i<n;++i)
	{
		if(x == is[i])
		{
			pos = i;
			break;
		}
	}
	return pos;
}

BtNode * CreatePI(ElemType *ps,ElemType *is,int n)  //前中序创建树
{
	BtNode *s = NULL;
	if(n > 0)
	{
		s = Buynode();
		s->data = ps[0];// s->data = *ps;
		int pos = FindPos(is,ps[0],n);
		if(pos == -1) exit(1);
		s->leftchild = CreatePI(ps+1,is,pos);
		s->rightchild = CreatePI(ps+1+pos,is+1+pos,n - pos - 1);
	}
	return s;
}

BtNode * CreateTreePI(ElemType *ps,ElemType *is,int n)  //前中序创建树
{
	if(NULL == ps || NULL == is || n < 1)
		return NULL;
	else
		return CreatePI(ps,is,n);
}

int main()
{
	char *ps = "ABCDEFGH";
	char *is = "CBEDFAGH";
	char *ls = "CEFDBHGA";
	int n = strlen(ps); // n = sizeof(ps);//
	BtNode *root = NULL;
	root = CreateTreePI(ps,is,n);
	return 0;
}

三、利用中后序遍历创建二叉树

int  FindPos(ElemType *is,ElemType x,int n)
{
	int pos = -1;
	for(int i = 0;i<n;++i)
	{
		if(x == is[i])
		{
			pos = i;
			break;
		}
	}
	return pos;
}

BtNode * CreateIL(ElemType *is,ElemType *ls,int n)  //中后序创建树
{
	BtNode *s = NULL;
	if(n > 0)
	{
		s = Buynode();
		s->data = ls[n-1];
		int pos = FindPos(is,ls[n-1],n);
		if(pos == -1) exit(1);
		s->leftchild = CreateIL(is,ls,pos);
		s->rightchild = CreateIL(is+pos+1,ls+pos,n - pos - 1);
	}
	return s;
}

BtNode * CreateTreeIL(ElemType *is,ElemType *ls,int n)//中后序创建树
{
	if(NULL == is || NULL == ls || n < 1) 
		return NULL;
	else
		return CreateIL(is,ls,n);
}

int main()
{
	char *ps = "ABCDEFGH";
	char *is = "CBEDFAGH";
	char *ls = "CEFDBHGA";
	int n = strlen(ps); // n = sizeof(ps);//
	BtNode* root = NULL;
	
	root = CreateTreeIL(is,ls,n);  //中后序
	return 0;
}