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binary_search_tree_iterator.cpp
49 lines (43 loc) · 1.03 KB
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binary_search_tree_iterator.cpp
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//12ms, 79.15%
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class BSTIterator {
public:
BSTIterator(TreeNode *root) {
TreeNode *tmp = root;
while(tmp){
_stack.push_back(tmp);
tmp = tmp->left;
}
}
/** @return whether we have a next smallest number */
bool hasNext() {
return _stack.size() != 0;
}
/** @return the next smallest number */
int next() {
TreeNode *tmp = _stack.back();
_stack.pop_back();
int ret = tmp->val;
tmp = tmp->right;
while(tmp != nullptr){
_stack.push_back(tmp);
tmp = tmp->left;
}
return ret;
}
private:
list<TreeNode *> _stack;
};
/**
* Your BSTIterator will be called like this:
* BSTIterator i = BSTIterator(root);
* while (i.hasNext()) cout << i.next();
*/