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by Sumit Chourasia | Oct 06, 2020 | Category :coding | Tags : algorithm binary-tree data-structure easy leetcode tree

Balanced Binary Tree - Tree - Easy - LeetCode

Balanced Binary Tree - Tree - Easy - LeetCode

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 left and right subtrees of every node differ in height by no more than 1.

 

Example 1:

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

    3
   / \
  9  20
    /  \
   15   7
Return true.

Example 2:

Given the following 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.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public bool IsBalanced(TreeNode root) {
        if(root==null){
            return true;
        }
        int left = Helper(root.left);
        int right = Helper(root.right);
        if(Math.Abs(left-right)>1){
            return false;
        }
        return IsBalanced(root.left)&&IsBalanced(root.right);
    }
    
    private int Helper(TreeNode root){
        if(root==null){
            return 0;
        }
        int left = Helper(root.left);
        int right = Helper(root.right);
        return 1+Math.Max(left,right);
    }
        
}

Time Complexity: O(n)

Space Complexity: O(1)

Contributed By: Sumit Chourasia
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