PAT(甲级)渡劫(二十四)-Root of AVL Tree (25)

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PAT(甲级)渡劫(二十四)-Root of AVL Tree (25)

代码如下：

#include <iostream>
#include <cstdio>
#include <cmath>

using namespace std;
struct TreeNode{
    int val;
    TreeNode *left,*right;
    TreeNode(int v):val(v),left(NULL),right(NULL){}
};

int height(TreeNode *r){
    return r == NULL?0:max(height(r->left),height(r->right))+1;
}
TreeNode *lRotate(TreeNode *r){
    TreeNode *p = r->right;
    r->right = p->left;
    p->left = r;
    return p;
}

TreeNode *rRotate(TreeNode *r){
    TreeNode *p = r->left;
    r->left = p->right;
    p->right = r;
    return p;
}
TreeNode *lrRotate(TreeNode *r){
    r->left = lRotate(r->left);
    return rRotate(r);
}
TreeNode *rlRotate(TreeNode *r){
    r->right = rRotate(r->right);
    return lRotate(r);
}
TreeNode *insert(int val,TreeNode *r){
    if(r == NULL) return new TreeNode(val);
    if(r->val < val){
        r->right = insert(val,r->right);
        if(abs(height(r->left)-height(r->right)) > 1){
            r = (r->right->val < val)?lRotate(r):rlRotate(r);
        }
    }else{
        r->left = insert(val,r->left);
        if(abs(height(r->left)-height(r->right)) > 1){
            r = (r->left->val > val)?rRotate(r):lrRotate(r);
        }
    }
    return r;
}

int main(){
    freopen("in.txt","r",stdin);
    TreeNode *r = NULL;
    int n;
    scanf("%d",&n);
    for(int i = 0 ; i < n ; i++){
        int val;
        scanf("%d",&val);
        r = insert(val,r);
    }
    printf("%d\n",r->val);
    return 0;
}

运行结果：