110. Balanced Binary Tree

Java

/**
 * Definition for a binary tree node.
 * 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;
        if(isTmp(root)<0) return false;
        return true;
    }
    
    public int isTmp(TreeNode root) {
        if(root==null) return 0;
        else
        {
            if(root.left!=null)
            root.left.val=isTmp(root.left)+1;
            if(root.right!=null)
            root.right.val=isTmp(root.right)+1;
            if(root.left!=null&&root.right!=null)
            {
                if(root.left.val-root.right.val>1||root.left.val-root.right.val<-1)
                return -1000;
                root.val=root.left.val>root.right.val?root.left.val:root.right.val;
            }
            else if(root.left==null&&root.right!=null)
            {
                if(root.right.val>1)
                return -1000;
                root.val=root.right.val;
            }
            else if(root.right==null&&root.left!=null)
            {
                if(root.left.val>1)
                return -1000;
                root.val=root.left.val;
            }
            else
            root.val=0;
        }
        return root.val;
    }
}

优解，Java，利用height来进行判断，比我写的简练

public boolean isBalanced(TreeNode root) {
    if(root==null){
        return true;
    }
    return height(root)!=-1;
    
}
public int height(TreeNode node){
    if(node==null){
        return 0;
    }
    int lH=height(node.left);
    if(lH==-1){
        return -1;
    }
    int rH=height(node.right);
    if(rH==-1){
        return -1;
    }
    if(lH-rH<-1 || lH-rH>1){
        return -1;
    }
    return Math.max(lH,rH)+1;
}