Leetcode | | 110. Balanced Binary Tree

Problem:

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

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

Hide TagsTree Depth-first SearchTest instructions: Judging whether a binary tree is a balanced binary tree

Thinking:

(1) This problem is very simple, but the careful study found that the balance of binary tree understanding is wrong: the maximum depth of the left and right sub-tree (that is, the height of the tree) is not more than 1,

Not specifically the height of each leaf node, the height of the tree. I started out by finding the height of each leaf node, and then comparing it to the definition of a balanced binary tree.

(2) The exact idea is to judge the left and right sub-trees at each time by recursion.

Code

Wrong idea:

Class Solution {    private:        vector<int> depth;    Public:       bool isbalanced (TreeNode *root) {            if (root==null)                return true;            DFS (0,root);           Sort (Depth.begin (), Depth.end ());           if (* (Depth.end ()-1)-depth[0]>1)               return false;                       else               return true;        }    Protected:        void dfs (int dep,treenode *node)        {            if (node==null)            {                cout<<dep<< Endl;                Depth.push_back (DEP);                return;            }            dep++;            DFS (dep,node->left);            DFS (dep,node->right);        }    };

Correct answer:

Class Solution {public  :      bool isbalanced (TreeNode *root) {          int depth = 0;          return isbalance (root, depth);                 }      BOOL Isbalance (TreeNode *root, int &depth)      {          if (root = = NULL)          {              depth = 0;              return true;          }          int ld,rd;          if (Isbalance (root->left,ld) && isbalance (root->right,rd))          {              if (ABS (LD-RD) > 1)              { C17/>return false;              }              depth = ld > RD? LD + 1:RD + 1;              return true;}}                ;

Leetcode | | 110. Balanced Binary Tree