leetcode

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173. Binary Search Tree Iterator

题目

Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.

Calling next() will return the next smallest number in the BST.

Example:

BSTIterator iterator = new BSTIterator(root);
iterator.next();    // return 3
iterator.next();    // return 7
iterator.hasNext(); // return true
iterator.next();    // return 9
iterator.hasNext(); // return true
iterator.next();    // return 15
iterator.hasNext(); // return true
iterator.next();    // return 20
iterator.hasNext(); // return false

Note:

• next() and hasNext() should run in average O(1) time and uses O(h) memory, where h is the height of the tree.
• You may assume that next() call will always be valid, that is, there will be at least a next smallest number in the BST when next() is called.

题目大意

实现一个二叉搜索树迭代器。你将使用二叉搜索树的根节点初始化迭代器。调用 next() 将返回二叉搜索树中的下一个最小的数。

解题思路

• 用优先队列解决即可

Documentation

Index

• type BSTIterator
  • func Constructor173(root *TreeNode) BSTIterator
  • func (this *BSTIterator) HasNext() bool
  • func (this *BSTIterator) Next() int
• type PriorityQueueOfInt
  • func (pq PriorityQueueOfInt) Len() int
  • func (pq PriorityQueueOfInt) Less(i, j int) bool
  • func (pq *PriorityQueueOfInt) Pop() interface{}
  • func (pq *PriorityQueueOfInt) Push(x interface{})
  • func (pq PriorityQueueOfInt) Swap(i, j int)
• type TreeNode

Types

type BSTIterator

type BSTIterator struct {
	// contains filtered or unexported fields
}

BSTIterator define

func Constructor173

func Constructor173(root *TreeNode) BSTIterator

Constructor173 define

func (*BSTIterator) HasNext

func (this *BSTIterator) HasNext() bool

* @return whether we have a next smallest number

func (*BSTIterator) Next

func (this *BSTIterator) Next() int

* @return the next smallest number

type PriorityQueueOfInt

type PriorityQueueOfInt []int

*

• Your BSTIterator object will be instantiated and called as such:
• obj := Constructor(root);
• param_1 := obj.Next();
• param_2 := obj.HasNext();

func (PriorityQueueOfInt) Len

func (pq PriorityQueueOfInt) Len() int

func (PriorityQueueOfInt) Less

func (pq PriorityQueueOfInt) Less(i, j int) bool

func (*PriorityQueueOfInt) Pop

func (pq *PriorityQueueOfInt) Pop() interface{}

func (*PriorityQueueOfInt) Push

func (pq *PriorityQueueOfInt) Push(x interface{})

func (PriorityQueueOfInt) Swap

func (pq PriorityQueueOfInt) Swap(i, j int)

type TreeNode

type TreeNode = structures.TreeNode

TreeNode define