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Commit 7283f65

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"Binary Search Tree Iterator"
1 parent 6321305 commit 7283f65

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‎README.md

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@@ -127,7 +127,7 @@ The `☢` means that you need to have a LeetCode Premium Subscription.
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| 186 | [Reverse Words in a String II] ☢ | |
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| 179 | [Largest Number] | [C](src/179.c) |
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| 174 | [Dungeon Game] | |
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| 173 | [Binary Search Tree Iterator] | |
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| 173 | [Binary Search Tree Iterator] | [C++](src/173.cpp) |
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| 172 | [Factorial Trailing Zeroes] | [C](src/172.c) |
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| 171 | [Excel Sheet Column Number] | [C](src/171.c) |
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| 170 | [Two Sum III - Data structure design] ☢ | |

‎src/173.cpp

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#include <iostream>
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#include <stack>
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using namespace std;
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struct TreeNode {
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int val;
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TreeNode *left;
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TreeNode *right;
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TreeNode(int x) : val(x), left(NULL), right(NULL) {}
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};
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class BSTIterator {
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stack<TreeNode *> path;
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public:
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BSTIterator(TreeNode *root) {
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while (root) {
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path.push(root);
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root = root->left;
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}
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}
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/** @return whether we have a next smallest number */
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bool hasNext() {
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return !path.empty();
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}
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/** @return the next smallest number */
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int next() {
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int ans = -1;
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if (hasNext()) {
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TreeNode *p = path.top();
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path.pop();
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ans = p->val;
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p = p->right;
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while (p) {
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path.push(p);
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p = p->left;
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}
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}
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return ans;
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}
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};
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int main() {
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/*
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* 5
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* / \
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* 2 7
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* / \ / \
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* 1 4 6 8
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* /
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* 3
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*/
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TreeNode *root = new TreeNode(5);
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root->left = new TreeNode(2);
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root->left->left = new TreeNode(1);
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root->left->right = new TreeNode(4);
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root->left->right->left = new TreeNode(3);
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root->right = new TreeNode(7);
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root->right->left = new TreeNode(6);
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root->right->right = new TreeNode(8);
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BSTIterator i = BSTIterator(root);
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while (i.hasNext()) cout << i.next();
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cout << endl;
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return 0;
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}

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