110. Balanced Binary Tree

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.

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判断一棵树是不是平衡二叉树。

public int height(TreeNode root) //求一个二叉树的高度
    {
        int right,left;
        if(root == null)
            return 0;
        left = height(root.left) + 1;
        right = height(root.right) + 1;
        return Math.max(left,right);
    }
    public boolean isBalanced(TreeNode root) {
        if(root == null)
            return true;
        int left = height(root.left);
        int right = height(root.right);
        int diff = left - right;  //如果一个子树高度差大于1
        if(diff < -1 || diff > 1)
            return false;
        return isBalanced(root.left) && isBalanced(root.right);
        
    }