1066. Root of AVL Tree (25)-PAT甲级真题

1066. Root of AVL Tree (25)
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

#include <cstdio>#define max(a, b) (((a) > (b)) ? (a) : (b))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;}