No.78 - LeetCode110 - 判断平衡树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int dfs(TreeNode* now,bool& ans,int level){
        int L,R;
        L = R = level;
        if(now->left != NULL) L = dfs(now->left,ans,level+1);
        if(now->right != NULL) R = dfs(now->right,ans,level+1);
        if(abs(L-R) > 1) ans = false;
        return max(L,R);
    }
    bool isBalanced(TreeNode* root) {
        if(root == NULL) return true;
        bool ans = true;
        dfs(root,ans,0);
        return ans;
    }
};