110.平衡二叉树

思路：

看左右的差绝对值是不是大于1

struct TreeNode {
	int val;
	TreeNode* left;
	TreeNode* right;
	TreeNode(int x) :val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
	bool BalanceTree(TreeNode* root) {
		return isBalance(root) != -1;
	}
	int isBalance(TreeNode* root) {
		if (root == NULL)return 0;
		int leftH = isBalance(root->left);
		if (leftH == -1)return -1;

		int rightH = isBalance(root->right);
		if (rightH == -1)return -1;

		if (abs(leftH - rightH) > 1) {
			return -1;
		}
		else {
			return 1 + max(leftH, rightH);
		}
	}
};

int main() {
	TreeNode* A = new TreeNode(3);
	TreeNode* B = new TreeNode(9);
	TreeNode* C = new TreeNode(20);
	TreeNode* D = new TreeNode(15);
	TreeNode* E = new TreeNode(7);
	A->left = B;
	A->right = C;
	C->left = D;
	C->right = E;
	Solution ss;
	cout << ss.BalanceTree(A) << endl;
	return 0;
}