int isBalancedCore(TreeNode* root){
if(root == NULL)
return 0;
int left = isBalancedCore(root->left);
int right = isBalancedCore(root->right);
if(left == -1 || right == -1)
return -1;
if(abs(left - right) <= 1)
return 1 + max(left, right);
else
return -1;
}
bool isBalanced(TreeNode *root) {
int res = isBalancedCore(root);
if(res == -1)
return false;
else
return true;
}
bool isBalanced_Solution2(BinaryTreeNode* pRoot)
{
if(pRoot == NULL)
{
return true;
}
int depth = 0;
return isBalancedCore(pRoot, &depth);
}
//方法二：采用后续遍历的方法，增加一个记录层次的变量，每个结点只遍历一次
bool isBalancedCore(BinaryTreeNode* pRoot, int* pDepth)
{
if(pRoot == NULL)
{
*pDepth = 0;
return true;
}
int left, right;
if(isBalancedCore(pRoot->m_pLeft, &left) && isBalancedCore(pRoot->m_pRight, &right))
{
int diff = left - right;
if(diff <= 1 && diff >= -1)
{
*pDepth = 1 + ((left > right) ? left : right);
return true;
}
}
return false;
}
