1066. Root of AVL Tree (25)
时间限制
100 ms
内存限制
65536 kB
代码长度限制
16000 B
判题程序
Standard
作者
CHEN, Yue
An AVL tree is a self-balancing binary search tree. In an AVL tree, the heights of the two child subtrees of any node differ by at most one; if at any time they differ by more than one, rebalancing is done to restore this property. Figures 1-4 illustrate the rotation rules.
Now given a sequence of insertions, you are supposed to tell the root of the resulting AVL tree.
Input Specification:
Each input file contains one test case. For each case, the first line contains a positive integer N (<=20) which is the total number of keys to be inserted. Then N distinct integer keys are given in the next line. All the numbers in a line are separated by a space.
Output Specification:
For each test case, print ythe root of the resulting AVL tree in one line.
Sample Input 1:
5
88 70 61 96 120
Sample Output 1:
70
Sample Input 2:
7
88 70 61 96 120 90 65
Sample Output 2:
88
代码如下：
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int n,index=0;
struct Node{
int key;
struct Node*left;
struct Node*right;
};
int getHeight(struct Node *tree){
if(tree==NULL){
return 0;
}
int l=getHeight(tree->left);
int r=getHeight(tree->right);
return l>r?l+1:r+1;
}
struct Node *leftRotate(struct Node*tree){
struct Node*temp=tree->right;
tree->right=temp->left;
temp->left=tree;
return temp;
}
struct Node *rightRotate(struct Node *tree){
struct Node*temp=tree->left;
tree->left=temp->right;
temp->right=tree;
return temp;
}
struct Node*leftRightRotate(struct Node*tree){
tree->left=leftRotate(tree->left);
tree=rightRotate(tree);
return tree;
}
struct Node*rightLeftRotate(struct Node*tree){
tree->right=rightRotate(tree->right);
tree=leftRotate(tree);
return tree;
}
struct Node* insert(struct Node*tree,int val){
if(tree==NULL){
tree=new struct Node();
tree->key=val;
return tree;
}
if(val<tree->key){
tree->left=insert(tree->left,val);
int l=getHeight(tree->left);
int r=getHeight(tree->right);
if(l-r>=2){
if(val<tree->left->key){
tree=rightRotate(tree);
}else{
tree=leftRightRotate(tree);
}
}
}else{
tree->right=insert(tree->right,val);
int l=getHeight(tree->left);
int r=getHeight(tree->right);
if(r-l>=2){
if(val>tree->right->key){
tree=leftRotate(tree);
}else{
tree=rightLeftRotate(tree);
}
}
}
return tree;
}
int main(){
scanf("%d",&n);
int value;
struct Node *tree=NULL;
for(int i=0;i<n;++i){
scanf("%d",&value);
tree=insert(tree,value);
}
printf("%d",tree->key);
return 0;
}
