PAT甲级-1066 Root of AVL Tree (25分)

点击链接PAT甲级-AC全解汇总

题目：
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 the 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

题意：
输出avl的root

虽然就25分的题，但是考察最基础的数据结构算法，还是很顶的
参考了算法笔记才写出来，论基本功的重要性

我的代码：

#include<bits/stdc++.h>
using namespace std;struct node{
    int v,height;node *lchild;node *rchild;
};node* newNode(int v){
    node* Node = new node;Node->v = v;Node->height = 1;Node->lchild = Node->rchild = NULL;return Node;
}int getheight(node* root){
    if(root == NULL) return 0;return root->height;
}int getbalancefactor(node* root){
    return getheight(root->lchild) - getheight(root->rchild);
}void updateheight(node* root){
    root->height = max(getheight(root->lchild),getheight(root->rchild)) + 1;
}void L(node* &root){
    node* temp = root->rchild;root->rchild = temp->lchild;temp->lchild = root;updateheight(root);updateheight(temp);root = temp;
}void R(node* &root){
    node* temp = root->lchild;root->lchild = temp->rchild;temp->rchild = root;updateheight(root);updateheight(temp);root = temp;
}void insert(node* &root,int v){
    if(root == NULL){
    root = newNode(v);return;}if(v <root->v){
    insert(root->lchild,v);updateheight(root);if(getbalancefactor(root) == 2){
    if(getbalancefactor(root->lchild) == 1){
    R(root);}else if(getbalancefactor(root->lchild) == -1){
    L(root->lchild);R(root);}}}else{
    insert(root->rchild,v);updateheight(root);if(getbalancefactor(root) == -2){
    if(getbalancefactor(root->rchild) == -1){
    L(root);}else if(getbalancefactor(root->rchild) == 1){
    R(root->rchild);L(root);}}}
}int main(){
    node* root = NULL;int N;cin>>N;for(int i=0;i<N;i++){
    int t;cin>>t;insert(root,t);}cout<<root->v<<endl;
}

面向测试点编程： 意外发现的，这位老哥实属优秀啊！

#include <bits/stdc++.h>
using namespace std;int main(int argc, char const *argv[])
{
    int n;cin >> n;int node[21];for (int i = 1; i <= n; ++i){
    cin >> node[i];}sort(node+1, node+n+1);if(n==11) cout << node[5] << endl;else if(n%2==0) cout << node[n/2+2] << endl;else cout << node[(n+1)/2] << endl;return 0;
}

原文链接：满分试探法