{ "data": { "question": { "questionId": "173", "questionFrontendId": "173", "boundTopicId": null, "title": "Binary Search Tree Iterator", "titleSlug": "binary-search-tree-iterator", "content": "
Implement the BSTIterator
class that represents an iterator over the in-order traversal of a binary search tree (BST):
BSTIterator(TreeNode root)
Initializes an object of the BSTIterator
class. The root
of the BST is given as part of the constructor. The pointer should be initialized to a non-existent number smaller than any element in the BST.boolean hasNext()
Returns true
if there exists a number in the traversal to the right of the pointer, otherwise returns false
.int next()
Moves the pointer to the right, then returns the number at the pointer.Notice that by initializing the pointer to a non-existent smallest number, the first call to next()
will return the smallest element in the BST.
You may assume that next()
calls will always be valid. That is, there will be at least a next number in the in-order traversal when next()
is called.
\n
Example 1:
\n\n\nInput\n["BSTIterator", "next", "next", "hasNext", "next", "hasNext", "next", "hasNext", "next", "hasNext"]\n[[[7, 3, 15, null, null, 9, 20]], [], [], [], [], [], [], [], [], []]\nOutput\n[null, 3, 7, true, 9, true, 15, true, 20, false]\n\nExplanation\nBSTIterator bSTIterator = new BSTIterator([7, 3, 15, null, null, 9, 20]);\nbSTIterator.next(); // return 3\nbSTIterator.next(); // return 7\nbSTIterator.hasNext(); // return True\nbSTIterator.next(); // return 9\nbSTIterator.hasNext(); // return True\nbSTIterator.next(); // return 15\nbSTIterator.hasNext(); // return True\nbSTIterator.next(); // return 20\nbSTIterator.hasNext(); // return False\n\n\n
\n
Constraints:
\n\n[1, 105]
.0 <= Node.val <= 106
105
calls will be made to hasNext
, and next
.\n
Follow up:
\n\nnext()
and hasNext()
to run in average O(1)
time and use O(h)
memory, where h
is the height of the tree?Compiled with clang 11
using the latest C++ 17 standard.
Your code is compiled with level two optimization (-O2
). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.
Most standard library headers are already included automatically for your convenience.
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Most standard library headers are already included automatically for your convenience.
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Python 2.7.12
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Most libraries are already imported automatically for your convenience, such as array, bisect, collections. If you need more libraries, you can import it yourself.
\\r\\n\\r\\nFor Map/TreeMap data structure, you may use sortedcontainers library.
\\r\\n\\r\\nNote that Python 2.7 will not be maintained past 2020. For the latest Python, please choose Python3 instead.
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Most standard library headers are already included automatically for your convenience.
\\r\\n\\r\\nFor hash table operations, you may use uthash. \\\"uthash.h\\\" is included by default. Below are some examples:
\\r\\n\\r\\n1. Adding an item to a hash.\\r\\n
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Your code is compiled with debug flag enabled (/debug
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Node.js 16.13.2
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Your code is run with --harmony
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lodash.js library is included by default.
\\r\\n\\r\\nFor Priority Queue / Queue data structures, you may use datastructures-js/priority-queue and datastructures-js/queue.
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Go 1.17.6
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Support https://godoc.org/github.com/emirpasic/gods library.
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Most libraries are already imported automatically for your convenience, such as array, bisect, collections. If you need more libraries, you can import it yourself.
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With bcmath module
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Your code is run with --harmony
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