用前序和中序建数和用中序和后序建数

 前序和中序建数

int Findvalue(char *is,Elemtype p,int n)
{
     for(int i = 0;i < n;++i)
	 {
		 if(is[i] == p)
			 return i;
	 }
	 return -1;
}
//根据前序和中序建立一个二叉树
BtNode *CreatePM(char *pr,char *is,int n)
{
	 Elemtype p = pr[0];
	 BtNode *tmp = NULL;
     if(n > 0)
	 {
		 int m = Findvalue(is,p,n);
		 if(-1 == m) exit(1);
		 tmp  = BuyNode();
		 tmp->data = p;
		 tmp->leftchild = CreatePM(pr+1,is,m);
		 tmp->rightchild = CreatePM(pr+m+1,is+m+1,n-m-1);
	
	 }
	 return tmp;
}

BtNode *CreatetreePM(char *pr,char *is,int n)
{
	  if(pr == NULL || is == NULL || n < 1) return NULL;
	  return  CreatePM(pr,is,n);
	  
}

用中序和后序建数

BtNode *CreateML(char *mi,char *la,int n)
{
	Elemtype p = la[n-1];
	BtNode *tmp = NULL;
	if(n > 0)
	{
		int m = Findvalue(mi,p,n);
		if(-1 == m) exit(1);
		tmp  = BuyNode();
		tmp->data = p;
		tmp->leftchild = CreateML(mi,la,m);
		tmp->rightchild = CreateML(mi+m+1,la+m,n-m-1);

	}
	return tmp;
}
BtNode *CreatetreeML(char *mi,char *la,int n)
{
	if(mi == NULL || la == NULL || n < 1) return NULL;
	return  CreateML(mi,la,n);

}