/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public boolean isBalanced(TreeNode root) { if(root==null) return true; int d1=depth(root.right); int d2=depth(root.left); if(Math.abs(d1-d2)>1) return false; else return isBalanced(root.left)&&isBalanced(root.right); } public int depth(TreeNode node) { if(node==null) return 0; int d1=depth(node.right); int d2=depth(node.left); int max=d1>d2?d1:d2; return max+1; } }
2.求高度的时候在不平衡的时候返回-1就ok了，不用求高度，但是效率好像没啥变化
/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { private boolean ans=true; public boolean isBalanced(TreeNode root) { if(root==null) return true; if(depth(root)==-1) return false; return true; } public int depth(TreeNode node) { if(node==null) return 0; int d1=depth(node.right); int d2=depth(node.left); if(d1==-1||d2==-1) return -1; if(Math.abs(d1-d2)>1) return -1; return Math.max(d1,d2)+1; } }
原文：http://www.cnblogs.com/hansongjiang/p/3856549.html
