Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
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非递归实现：
int maxDepth(TreeNode* root) {
int maxDepth = ;
if (root == nullptr)
return maxDepth;
stack<TreeNode*> sta;
sta.push(root);
TreeNode* lastRoot = root;
while (!sta.empty())
{
root = sta.top();
if (lastRoot != root->right)
{
if (lastRoot != root->left) {
if (root->left != nullptr) {
sta.push(root->left);
continue;
}
}
if (root->right != nullptr) {
sta.push(root->right);
continue;
}
maxDepth = sta.size() > maxDepth ? sta.size() : maxDepth;
}
lastRoot = root;
sta.pop();
}
return maxDepth;
}
递归实现：
int maxDepth(TreeNode* root) {
if (root == nullptr)
return ;
int leftDepth = maxDepth(root->left) + ;
int rightDepth = maxDepth(root->right) + ;
return leftDepth > rightDepth ? leftDepth : rightDepth;
}