PAT 甲级 1066 Root of AVL Tree

https://pintia.cn/problem-sets/994805342720868352/problems/994805404939173888

 

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 Ndistinct 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

 

代码：

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#include <bits/stdc++.h> using namespace std; struct node {     int val;     struct node *left, *right; }; node *rotateLeft(node *root) {     node *t = root -> right;     root -> right = t -> left;     t -> left = root;     return t; }   node *rotateRight(node *root) {     node *t = root -> left;     root -> left = t -> right;     t -> right = root;     return t; }   node *rotateLeftRight(node *root) {     root -> left = rotateLeft(root -> left);     return rotateRight(root); }   node *rotateRightLeft(node *root) {     root -> right = rotateRight(root -> right);     return rotateLeft(root); }   int getHeight(node *root) {     if(root == NULL) return 0;     return max(getHeight(root -> left), getHeight(root -> right)) + 1; }   node *insert(node *root, int val) {     if(root == NULL) {         root = new node();         root -> val = val;         root -> left = root -> right = NULL;     } else if(val < root -> val) {         root -> left = insert(root -> left, val);         if(getHeight(root -> left) - getHeight(root -> right) == 2)             root = val < root -> left -> val ? rotateRight(root) : rotateLeftRight(root);     } else {         root -> right = insert(root -> right, val);         if(getHeight(root -> left) - getHeight(root -> right) == -2)             root = val > root -> right -> val ? rotateLeft(root) : rotateRightLeft(root);     }     return root; }   int main() {     int n, val;     scanf("%d", &n);     node *root = NULL;     for(int i = 0; i < n; i ++) {         scanf("%d", &val);         root = insert(root, val);     }     printf("%d", root -> val);     return 0; }

　　AVL 树的模板题 第一次写 AVL 树 还不是很会 还有那么多题没写 不会的越来越多？烦