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BSTIterator.cpp
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53 lines (48 loc) · 1.04 KB
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/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
stack<TreeNode*> st;
TreeNode* curr = NULL;
BSTIterator::BSTIterator(TreeNode *root) {
while(!st.empty()){
st.pop();
}
curr = root;
while(curr != NULL){
st.push(curr);
curr = curr->left;
}
}
/** @return whether we have a next smallest number */
bool BSTIterator::hasNext() {
if(st.empty()){
return false;
}
return true;
}
/** @return the next smallest number */
int BSTIterator::next() {
if(st.empty()){
return -1;
}
curr = st.top();
int ans = curr->val;
curr = curr->right;
st.pop();
while(curr != NULL){
st.push(curr);
curr = curr->left;
}
return ans;
}
/**
* Your BSTIterator will be called like this:
* BSTIterator i = BSTIterator(root);
* while (i.hasNext()) cout << i.next();
*/