Sicily 3825. AVL Tree

万恶的AVL树，我只是想为机考热热身……虽然说对于AVL树只求理解不求实现，但既然碰到了，还是力求AC吧。就这样，做了整整一天（我才刚摆脱那邪恶的一万字英语论文……）
AVL树，书上和百度百科的代码都很长，而且书上的用了继承，百度百科的没有缩进，烦，没看。按照自己的理解慢慢写，但一直都程序崩溃，就像同时的选课系统崩溃一样。崩溃的原因费了很大精力，还是只能定位在旋转这个过程上而已。个人感觉是在指针引用上的处理不当引起的，虽然说我怎么也看不出具体问题所在，断点调试跟踪各种办法试遍，却都得到一个很怪异的情况：指针引用的赋值执行了，却没有实现，并且这个过程发生在函数内，貌似不关引用的事，具体原因不详……
最后决定在旋转这个过程中放弃使用引用，然后增设父母节点，改了很多，还是不成功；后来用栈代替递归，其他内容原封不动，结果AC了。
AC的代码很麻烦，若能实现递归的话会简明很多。

Run Time: 0sec

Run Memory: 312KB

Code length: 2570Bytes

Submit Time: 2012-01-05 21:56:44

// Problem#: 3825
// Submission#: 1175812
// The source code is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
// URI: http://creativecommons.org/licenses/by-nc-sa/3.0/
// All Copyright reserved by Informatic Lab of Sun Yat-sen University
#include <iostream>
#include <stack>
using namespace std;

struct Node {
    int data;
    Node *left, *right;
    Node( int n ) { data = n; left = NULL; right = NULL; }
};

Node *root;
stack<Node*> s;

int getHeight( Node *sub );
void insert( Node* &sub, int data );
void rotLeft( Node *sub, Node *parent );
void rotRight( Node *sub, Node *parent );
void balance();
void preorder( Node *sub );
void release( Node* &sub );

int main()
{
    int t;
    int n, data;

    cin >> t;
    while ( t-- ) {
        root = NULL;
        cin >> n;
        while ( n-- ) {
            cin >> data;
            insert( root, data );
            balance();
        }
        preorder( root );
        cout << endl;
        release( root );
    }

    return 0;

}


int getHeight( Node* sub ) {
    return sub != NULL ? 1 + max( getHeight( sub->left ), getHeight( sub->right ) ): 0;
}

void insert( Node* &sub, int data ) {
    if ( sub != NULL ) {
        s.push( sub );
        insert( data < sub->data ? sub->left: sub->right, data );
    }
    else
        sub = new Node( data );
}

void rotLeft( Node *sub, Node *parent ) {
    Node *right = sub->right;
    sub->right = right->left;
    right->left = sub;
    if ( parent == NULL )
        root = right;
    else
        sub == parent->left ? parent->left = right: parent->right = right;
}

void rotRight( Node *sub, Node *parent ) {
    Node *left = sub->left;
    sub->left = left->right;
    left->right = sub;
    if ( parent == NULL )
        root = left;
    else
        sub == parent->left ? parent->left = left: parent->right = left;
}

void balance() {
    Node *sub;
    while ( !s.empty() ) {
        sub = s.top();
        s.pop();
        int LHeight = getHeight( sub->left );
        int RHeight = getHeight( sub->right );
        if ( LHeight - RHeight == 2 ) {
            if ( getHeight( sub->left->right ) - getHeight( sub->left->left ) == 1 )
                rotLeft( sub->left, sub );
            rotRight( sub, s.empty() ? NULL: s.top() );
        }
        else if ( RHeight - LHeight == 2 ) {
            if ( getHeight( sub->right->left ) - getHeight( sub->right->right ) == 1 )
                rotRight( sub->right, sub );
            rotLeft( sub, s.empty() ? NULL: s.top() );
        }
    }
}

void preorder( Node *sub ) {
    if ( sub != NULL ) {
        cout << sub->data << " ";
        preorder( sub->left );
        preorder( sub->right );
    }
}

void release( Node* &sub ) {
    if ( sub != NULL ) {
        release( sub->left );
        release( sub->right );
        delete sub;
    }
}