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binary-search-tree-iterator.cpp
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48 lines (43 loc) · 1.02 KB
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/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class BSTIterator {
private:
stack<TreeNode *>st;
void _push(TreeNode *n)
{
while(n)
{
st.push(n);
n=n->left;
}
}
public:
BSTIterator(TreeNode* root) {
_push(root);
}
int next() {
TreeNode *n;
n=st.top();
st.pop();
_push(n->right);
return n->val;
}
bool hasNext() {
return !st.empty();
}
};
/**
* Your BSTIterator object will be instantiated and called as such:
* BSTIterator* obj = new BSTIterator(root);
* int param_1 = obj->next();
* bool param_2 = obj->hasNext();
*/