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  • LeetCode

    Balanced Binary Tree

    2014.1.8 04:09

    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.

    Solution:

      Just do as the problem says, calculate the heights and check if they meet the requirement.

      Time complexity is O(n), where n is the number of nodes in the tree. Space complexity is O(1).

    Accepted code:

     1 // 1AC, good~
     2 /**
     3  * Definition for binary tree
     4  * struct TreeNode {
     5  *     int val;
     6  *     TreeNode *left;
     7  *     TreeNode *right;
     8  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
     9  * };
    10  */
    11 class Solution {
    12 public:
    13     bool isBalanced(TreeNode *root) {
    14         // IMPORTANT: Please reset any member data you declared, as
    15         // the same Solution instance will be reused for each test case.
    16         if(root == nullptr){
    17             return true;
    18         }
    19         
    20         return myabs(treeHeight(root->left) - treeHeight(root->right)) <= 1 && isBalanced(root->left) && isBalanced(root->right);
    21     }
    22 private:
    23     const int &myabs(const int &num) {
    24         return (num >= 0 ? num : -num);
    25     }
    26     
    27     const int &mymax(const int &x, const int &y) {
    28         return (x > y ? x : y);
    29     }
    30     
    31     int treeHeight(TreeNode *root) {
    32         if(root == nullptr){
    33             return 0;
    34         }else{
    35             return mymax(treeHeight(root->left), treeHeight(root->right)) + 1;
    36         }
    37     }
    38 };
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  • 原文地址:https://www.cnblogs.com/zhuli19901106/p/3510002.html
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