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simple_110_BalancedBinaryTree.java
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72 lines (66 loc) · 1.46 KB
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/**
* created by zl on 2019/3/28 7:44
*
* 给定一个二叉树，判断它是否是高度平衡的二叉树。
*
* 本题中，一棵高度平衡二叉树定义为：
*
* 一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过1。
*
* 示例 1:
*
* 给定二叉树 [3,9,20,null,null,15,7]
*
* 3
* / \
* 9 20
* / \
* 15 7
* 返回 true 。
*
* 示例 2:
*
* 给定二叉树 [1,2,2,3,3,null,null,4,4]
*
* 1
* / \
* 2 2
* / \
* 3 3
* / \
* 4 4
* 返回 false 。
*/
public class simple_110_BalancedBinaryTree
{
/* public boolean isBalanced(TreeNode root)
{
if(root == null)
return true;
return isBalanced(root.left)
&& isBalanced(root.right)
&& Math.abs(depth(root.left) - depth(root.right)) <= 1;
}
private int depth(TreeNode root)
{
if(root == null)
return 0;
return 1+Math.max(depth(root.left),depth(root.right));
}*/
public boolean isBalanced(TreeNode root) {
return depth(root) != -1;
}
private int depth(TreeNode root) {
if (root == null)
return 0;
int left = depth(root.left);
if (left == -1)
return -1;
int right = depth(root.right);
if (right == -1)
return -1;
if (Math.abs(left - right) > 1)
return -1;
return Math.max(left, right) + 1;
}
}