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:
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AC:
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最后的判断条件是该节点的左子树右子树高度差不超过1， 并且左子树和右子树也都是 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;
}
}
