Easy
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.
submit 1:
Screen Shot 2017-09-02 at 9.23.01 AM.png
AC:
Screen Shot 2017-09-02 at 9.21.14 AM.png
最后的判斷條件是該節(jié)點的左子樹右子樹高度差不超過1鳄橘， 并且左子樹和右子樹也都是 Balanced Binary Tree.
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isBalanced(TreeNode root) {
if (root == null){
return true;
}
int diff = Math.abs(helper(root.left) - helper(root.right));
if (diff > 1){
return false;
}
return isBalanced(root.left) && isBalanced(root.right);
}
private int helper(TreeNode head){
if (head == null){
return 0;
}
if (head.left == null && head.right == null){
return 1;
}
return Math.max(helper(head.left), helper(head.right)) + 1;
}
}
