题解 | #判断是不是平衡二叉树#

后序遍历，同时计算深度和判断是否为平衡树

class Solution {
public:
    bool IsBalanced_Solution(TreeNode* pRoot) {
        return depth(pRoot) != -1;
    }
    int depth(TreeNode* root) {
        if(!root) return 0;
        int l = depth(root->left);
        if(l == -1) return -1;
        int r = depth(root->right);
        if(r == -1) return -1;
        int sub = abs(l - r);
        if(sub > 1) return -1;
        return max(l, r) + 1;
    }
};