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;

}