NO.110 balanced binary tree

Given a binary tree to determine whether it is a highly balanced binary tree.

In this problem, a highly balanced binary tree is defined as:

    An absolute value of a binary tree height difference between left and right subtrees of each node is not more than 1.

Example 1:

Given binary tree [3,9,20, null, null, 15,7]

    3
   / \
  9  20
    /  \
   15   7

Return true.

Example 2:

Given binary tree [1,2,2,3,3, null, null, 4,4]

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4

Return false.

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */

int DFS(struct TreeNode* root)
{
    if(!root)return 0;
    int left=0,right=0;
    if(root->left)left=DFS(root->left);
    if(root->right)right=DFS(root->right);
    if(left<0||right<0||abs(left-right)>1)return -2;
    else return left>right?left+1:right+1;
}

bool isBalanced(struct TreeNode* root){
    return DFS(root)>=0;
}

When execution: 8 ms, beat the 99.63% of all users in C submission

Memory consumption: 10.1 MB, defeated 100.00% of all users in C submission