04-树5 Root of AVL Tree

#include 
#include 


typedef int ElementType;
typedef struct AVLNode *AVLTree; /* AVL树类型 */
typedef struct AVLNode{
    ElementType Data; /* 结点数据 */
    AVLTree Left;     /* 指向左子树 */
    AVLTree Right;    /* 指向右子树 */
    int Height;       /* 树高 */
}AVLNode;


int Max ( int a, int b );
int GetHeight(AVLTree T);
AVLTree SingleLeftRotation ( AVLTree A );
AVLTree DoubleLeftRightRotation ( AVLTree A );
AVLTree SingleRightRotation ( AVLTree A );
AVLTree DoubleRightLeftRotation ( AVLTree A );
AVLTree Insert( AVLTree T, ElementType X );


int main(int argc, char const *argv[])
{
	// freopen("test.txt", "r", stdin);
	int N, tmp;
	scanf("%d", &N);
	AVLTree AVL = NULL;
	for (int i = 0; i < N; ++i){
		scanf("%d", &tmp);
		AVL = Insert(AVL, tmp);
	}
	printf("%d\n", AVL->Data);
	return 0;
}
 
int Max ( int a, int b )
{
    return a > b ? a : b;
}


int GetHeight(AVLTree T)
{
	if(!T)
		return 0;
	else
		return T->Height;
}
 
AVLTree SingleLeftRotation ( AVLTree A )
{ /* 注意：A必须有一个左子结点B */
  /* 将A与B做左单旋，更新A与B的高度，返回新的根结点B */     
 
    AVLTree B = A->Left;
    A->Left = B->Right;
    B->Right = A;
    A->Height = Max( GetHeight(A->Left), GetHeight(A->Right) ) + 1;
    B->Height = Max( GetHeight(B->Left), A->Height ) + 1;
  
    return B;
}
 
AVLTree DoubleLeftRightRotation ( AVLTree A )
{ /* 注意：A必须有一个左子结点B，且B必须有一个右子结点C */
  /* 将A、B与C做两次单旋，返回新的根结点C */
     
    /* 将B与C做右单旋，C被返回 */
    A->Left = SingleRightRotation(A->Left);
    /* 将A与C做左单旋，C被返回 */
    return SingleLeftRotation(A);
}


AVLTree SingleRightRotation ( AVLTree A )
{
	AVLTree B = A->Right;
	A->Right = B->Left;
	B->Left = A;
	A->Height = Max( GetHeight(A->Left), GetHeight(A->Right) ) + 1;
	B->Height = Max( GetHeight(B->Right), A->Height) + 1;


	return B;
}


AVLTree DoubleRightLeftRotation ( AVLTree A )
{
	A->Right = SingleLeftRotation(A->Right);
	return SingleRightRotation(A);
}


AVLTree Insert( AVLTree T, ElementType X )
{ /* 将X插入AVL树T中，并且返回调整后的AVL树 */
    if ( !T ) { /* 若插入空树，则新建包含一个结点的树 */
        T = (AVLTree)malloc(sizeof(struct AVLNode));
        T->Data = X;
        T->Height = 0;
        T->Left = T->Right = NULL;
    } /* if (插入空树) 结束 */
 
    else if ( X < T->Data ) {
        /* 插入T的左子树 */
        T->Left = Insert( T->Left, X);
        /* 如果需要左旋 */
        if ( GetHeight(T->Left)-GetHeight(T->Right) == 2 )
            if ( X < T->Left->Data ) 
               T = SingleLeftRotation(T);      /* 左单旋 */
            else 
               T = DoubleLeftRightRotation(T); /* 左-右双旋 */
    } /* else if (插入左子树) 结束 */
     
    else if ( X > T->Data ) {
        /* 插入T的右子树 */
        T->Right = Insert( T->Right, X );
        /* 如果需要右旋 */
        if ( GetHeight(T->Left)-GetHeight(T->Right) == -2 )
            if ( X > T->Right->Data ) 
               T = SingleRightRotation(T);     /* 右单旋 */
            else 
               T = DoubleRightLeftRotation(T); /* 右-左双旋 */
    } /* else if (插入右子树) 结束 */
 
    /* else X == T->Data，无须插入 */
 
    /* 更新树高 */
    T->Height = Max( GetHeight(T->Left), GetHeight(T->Right) ) + 1;
     
    return T;
}