标签：__init__ search http user calling creat tco ISE tps
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.
Note: next() and hasNext() should run in average O(1) time and uses O(h) memory, where h is the height of the tree.
Credits:
Special thanks to @ts for adding this problem and creating all test cases.
Approach #1: C++.
/**
* 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) {
helper(root);
}
/** @return whether we have a next smallest number */
bool hasNext() {
if (minNums.empty()) return false;
else return true;
}
/** @return the next smallest number */
int next() {
TreeNode* cur = minNums.top();
minNums.pop();
helper(cur->right);
return cur->val;
}
private:
stack<TreeNode*> minNums;
void helper(TreeNode* root) {
while (root != nullptr) {
minNums.push(root);
root = root->left;
}
}
};
/**
* Your BSTIterator will be called like this:
* BSTIterator i = BSTIterator(root);
* while (i.hasNext()) cout << i.next();
*/
Approach #2: Java.
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class BSTIterator {
public BSTIterator(TreeNode root) {
helper(root);
}
/** @return whether we have a next smallest number */
public boolean hasNext() {
if (stack.isEmpty()) return false;
return true;
}
/** @return the next smallest number */
public int next() {
TreeNode cur = stack.pop();
helper(cur.right);
return cur.val;
}
private Stack<TreeNode> stack = new Stack<TreeNode>();
private void helper(TreeNode root) {
while (root != null) {
stack.push(root);
root = root.left;
}
}
}
/**
* Your BSTIterator will be called like this:
* BSTIterator i = new BSTIterator(root);
* while (i.hasNext()) v[f()] = i.next();
*/
Approach #3: Python.
# Definition for a binary tree node
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class BSTIterator(object):
def __init__(self, root):
"""
:type root: TreeNode
"""
self.stack = list()
self.helper(root)
def hasNext(self):
"""
:rtype: bool
"""
return self.stack
def next(self):
"""
:rtype: int
"""
cur = self.stack.pop()
self.helper(cur.right)
return cur.val
def helper(self, root):
while root is not None:
self.stack.append(root)
root = root.left
# Your BSTIterator will be called like this:
# i, v = BSTIterator(root), []
# while i.hasNext(): v.append(i.next())
标签：__init__ search http user calling creat tco ISE tps
原文地址：https://www.cnblogs.com/ruruozhenhao/p/10011307.html
