Root of AVL Tree (25)

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题目地址：http://www.patest.cn/contests/pat-a-practise/1066

需要重点掌握平衡二叉树的4种旋转（LL RR LR RL )
注意树高度要跟着调整
学习网址：
http://www.cnblogs.com/huangxincheng/archive/2012/07/22/2603956.html
http://www.cnblogs.com/guyan/archive/2012/09/03/2668399.html

/*Root of AVL Tree (25)http://www.patest.cn/contests/pat-a-practise/1066*/#include <cstdio>  #include <sstream>  #include <cstring>  #include <iostream>#include <string>#include <vector>#include <queue>#include <algorithm>#include <sstream>#include <cmath>#include <set>#include <map>#include <unordered_map>#include <stack>using namespace std;int n;typedef struct node{    int data;    int height;    struct node* left;    struct node* right;    node(int _data = -1)    {        data = _data;        height = 0;        left = NULL;        right = NULL;    }}Bnode;int max2(int a, int b){    return a > b ? a : b;}int getHeight(Bnode* root){    if (root == NULL)        return 0; //return -1 也行    return root->height;}bool isbalance(Bnode* root){    int k = abs(getHeight(root->left) - getHeight(root->right));    if (k < 2)        return true;    return false;}// 调整高度 : 左子树的高度 右子树的高度取最大 加上1  就行了 int UpdateHeight(Bnode* root){    return max2(getHeight(root->left), getHeight(root->right)) + 1;}Bnode* LL(Bnode* root){    Bnode* tmpL = root->left;    root->left = tmpL->right;    tmpL->right = root;    root->height = UpdateHeight(root);//先调整root , 再调整 tmpL    tmpL->height = UpdateHeight(tmpL);     return tmpL;}Bnode* RR(Bnode* root){    Bnode* tmpL = root->right;    root->right = tmpL->left;    tmpL->left = root;    root->height = UpdateHeight(root);    tmpL->height = UpdateHeight(tmpL);    return tmpL;}Bnode* LR(Bnode* root){    Bnode* tmpL = root->left;    root->left = RR(tmpL);    return LL(root);}Bnode* RL(Bnode* root){    Bnode* tmpL = root->right;    root->right = LL(tmpL);    return RR(root);}Bnode* createTree(Bnode* root, int data){    if (root != NULL)    {        if (data < root->data) // left        {            root->left = createTree(root->left, data);            if (!isbalance(root))            {                if (data < root->left->data) // LL                {                    root = LL(root);                }                else{   // LR                    root = LR(root);                }            }        }        else{ // right             root->right = createTree(root->right, data);            if (!isbalance(root))            {                if (data > root->right->data) // RR                {                    root = RR(root);                }                else{   // RL                    root = RL(root);                }            }        }    }    else{        root = new node(data);    }    root->height = UpdateHeight(root); //max2(getHeight(root->left), getHeight(root->right)) + 1;    return root;}int main(){    //freopen("in", "r", stdin);    while (scanf("%d", &n) != EOF)    {        Bnode *root = NULL;        int i, tmp;        root = NULL;        for (i = 0; i < n; i++)        {            scanf("%d", &tmp);            root = createTree(root, tmp);        }        cout << root->data << endl;    }    return 0;}

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