isBalanced.cc

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    public:
        bool isBalanced(TreeNode *root) {
        if (!root) return true;
        int h;
        return _isBal(root, h);
    }
    
    bool _isBal(TreeNode *root, int &h) {
        if (!root) {
            h = 0;
            return true;
        }
        int h1, h2;
        bool l = _isBal(root->left, h1);
        bool r = _isBal(root->right, h2);
        h = max(h1, h2) + 1;
        if (l && r && (abs(h1 - h2) <= 1)) return true;
        else return false;
    }
    //--------------------------------------//
    bool ret = true; 
    bool isBalanced(TreeNode *root) {
        if (!root) return true;
        int left = depth(root->left);
        int right = depth(root->right);
        if (abs(left - right) > 1) return false;
        else return ret;
    }
    
    int depth(TreeNode *root) {
        if (!root) return 0;
        int left = depth(root->left);
        int right = depth(root->right);
        if (abs(left - right) > 1) ret = false;
        return max(left, right) + 1;
    }
    /*bool isBalanced(TreeNode *root) {
        if (!root) return true;
        int left = depth(root->left);
        int right = depth(root->right);
        if (abs(left - right) > 1) return false;
        return isBalanced(root->left) && isBalanced(root->right);
    }
    int depth(TreeNode *root) {
        if (!root) return 0;
        int left = depth(root->left);
        int right = depth(root->right);
        return left > right ? left + 1 : right + 1;
    }*/
};