leetcode:Balanced Binary Tree

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution{
private:
	bool balanced=true;
	int treeDepth(TreeNode *root)
	{
		int depth=0;
		int leftDepth=0;
		int rightDepth=0;
		
		if(root==NULL)
			return 0;
			
		leftDepth=treeDepth(root->left)+1;
		rightDepth=treeDepth(root->right)+1;
		if(leftDepth==-1||rightDepth==-1)
		    return -1;
		if(abs(leftDepth-rightDepth)>1)
			  return -1;
		depth=leftDepth>rightDepth?leftDepth:rightDepth;
		return depth;
	}
public:
	 bool isBalanced(TreeNode *root) 
	 {
		 int depth=treeDepth(root);
	    if(depth==-1)
	        return false;
	   else
	    return true;
	 }
};