C语言实现由遍历序列构造二叉树

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_17497931/article/details/84025755

 程序需要包含二叉树的基本运算算法，我在之前的文章中已经写过，详见：C语言实现二叉树各种基本运算的算法

#define "btree.cpp"    //包含二叉树的基本运算算法，详见文章顶部链接
#define MaxWidth 40

/* 由中序遍历序列构造二叉树 */
BTNode * CreateBT1( char * pre, char * in, int n )
{
	BTNode	*b;
	char	*p;
	int	k;
	if ( n <= 0 )
		return(NULL);
	b	= (BTNode * ) malloc( sizeof(BTNode) );
	b->data = *pre;
	for ( p = in; p < in + n; p++ )
		if ( *p == *pre )
			break;
	k		= p - in;
	b->lchild	= CreateBT1( pre + 1, in, k );
	b->rchild	= CreateBT1( pre + k + 1, p + 1, n - k - 1 );
	return(b);
}


/* 由中序和后序遍历序列构造二叉树 */
BTNode * CreateBT2( char * post, char * in, int n )
{
	BTNode	* b;
	char	r, *p;
	int	k;
	if ( n <= 0 )
		return(NULL);
	r	= *(post + n - 1);
	b	= (BTNode *) malloc( sizeof(BTNode) );
	b->data = r;
	for ( p = in; p < in + n; p++ )
		if ( *p == r )
			break;
	k		= p - in;
	b->lchild	= CreateBT2( post, in, k );
	b->rchild	= CreateBT2( post + k, p + 1, n - k - 1 );
	return(b);
}


/* 以凹入表示法输出一颗二叉树 */
void DispBTree1( BTNode *b )
{
	BTNode	*St[MaxSize], *p;
	int	level[MaxSize][2], top = -1, n, i, width = 4;
	char	type;
	if ( b != NULL )
	{
		top++;
		St[top]		= b;
		level[top][0]	= width;
		level[top][1]	= 2;
		while ( top > -1 )
		{
			p	= St[top];
			n	= level[top][0];
			switch ( level[top][1] )
			{
			case 0: type	= 'L'; break;
			case 1: type	= 'R'; break;
			case 2: type	= 'B'; break;
			}
			for ( i = 1; i <= n; i++ )
				printf( " " );
			printf( "%c(%c)", p->data, type );
			for ( i = n + 1; i <= MaxWidth; i += 2 )
				printf( "--" );
			printf( "\n" );
			top--;
			if ( p->rchild != NULL )
			{
				top++;
				St[top]		= p->rchild;
				level[top][0]	= n + width;
				level[top][1]	= 1;
			}
			if ( p->lchild != NULL )
			{
				top++;
				St[top]		= p->lchild;
				level[top][0]	= n + width;
				level[top][1]	= 0;
			}
		}
	}
}


int main()
{
	BTNode		*b;
	ElemType	pre[]	= "ABDEHJKLMNCFGI";
	ElemType	in[]	= "DBJHLKMNEAFCGI";
	ElemType	post[]	= "DJLNMKHEBFIGCA";
	int		n	= 14;
	b = CreateBT1( pre, in, n );
	printf( "先序序列：%s\n", pre );
	printf( "中序序列：%s\n", in );
	printf( "构造一颗二叉树b：\n" );
	printf( "	括号表示法：");
	DispBTree( b );
	printf( "\n" );
	printf( "	凹入表示法：\n");
	DispBTree1( b );
	printf( "\n\n" );
	printf( "中序序列：%s\n", in );
	printf( "后序序列：%s\n", post );
	printf( "	括号表示法：");
	DispBTree( b );
	printf( "\n" );
	printf( "	凹入表示法：\n");
	DispBTree1( b );
	printf( "\n" );
	DispBTree( b );
	return(1);
}