110. Balanced Binary Tree

系统管理员 2022-03-26 08:59 310阅读 0赞

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.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

  1. 3
  2.    / \
  3.   9  20
  4.     /  \
  5.    15   7

Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

  1. 1
  2.       / \
  3.      2   2
  4.     / \
  5.    3   3
  6.   / \
  7.  4   4

Return false.

  1. /**
  2.  * Definition for a binary tree node.
  3.  * struct TreeNode {
  4.  *     int val;
  5.  *     TreeNode *left;
  6.  *     TreeNode *right;
  7.  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  8.  * };
  9.  */
  10. class Solution {
  11. public:
  12.     bool isBalanced(TreeNode* root) {
  13.       if(root == NULL)
  14.          return true;
  16.       int lLen = GetLength(root->left);
  17.       int rLen = GetLength(root->right);
  18.       if(abs(lLen-rLen)>1)
  19.           return false;
  21.         return  isBalanced(root->left) && isBalanced(root->right);
  22.     }
  23. private:
  24.  int GetLength(TreeNode* root)
  25.  {
  26.     if(root == NULL)
  27.          return 0;
  28.     int lLen = GetLength(root->left);
  29.     int rLen = GetLength(root->right);
  30.     int maxLen = lLen>rLen?lLen:rLen;
  31.     return maxLen + 1;
  32.  }
  33. };

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