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Balanced Binary Tree (二叉树DFS)

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

判断一棵树是否为平衡二叉树。

思路:典型的递归,从第一个根节点开始,看左子树和右子树的深度差值是否小于等于1,然后再看由根节点的左孩子和右孩子构成的两课树是否都符合条件。

代码:

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {private:    int maxdepth;public:    void solve(TreeNode *root,int depth){        if(root==NULL)            return;        if(depth>maxdepth)            maxdepth=depth;        solve(root->left,depth+1);        solve(root->right,depth+1);    }    int getDepth(TreeNode *root) {        maxdepth=0;        solve(root,1);        return maxdepth;    }    bool isBalanced(TreeNode *root) {        if(root==NULL)             return true;        int l,r;        if(root->left!=NULL){            l=getDepth(root->left);        }else{            l=0;        }        if(root->right!=NULL){            r=getDepth(root->right);        }else{            r=0;        }        return abs(l-r)<=1&&isBalanced(root->left)&&isBalanced(root->right);    }};

 

Balanced Binary Tree (二叉树DFS)