careercup-树与图 4.1

4.1 实现一个函数，检查二叉树是否平衡。在这个问题中，平衡树的定义如下：任意一个结点，其两颗子树的高度差不超过1.

C++实现代码：

#include<iostream>
#include<new>
#include<cmath>
using namespace std;

//Definition for binary tree
struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

void createTree(TreeNode *&root)
{
    int i;
    cin>>i;
    if(i!=0)
    {
        TreeNode *tmp=new TreeNode(i);
        root=tmp;
        createTree(root->left);
        createTree(root->right);
    }
}

int high(TreeNode *root)
{
    if(root==NULL)
        return 0;
    if(root->left==NULL&&root->right)
        return 1;
    int lhigh=high(root->left);
    int rhigh=high(root->right);
    return (lhigh>=rhigh)?lhigh+1:rhigh+1;
}

bool isAVL(TreeNode *root)
{
    if(root==NULL)
        return true;
    if(root->left==NULL&&root->right==NULL)
        return true;
    int lhigh=high(root->left);
    int rhigh=high(root->right);
    if(abs(lhigh-rhigh)<2)
        return isAVL(root->left)&&isAVL(root->right);
    return false;
}

int main()
{
    TreeNode *root=NULL;
    createTree(root);
    cout<<high(root)<<endl;
    cout<<isAVL(root)<<endl;
}