标签：calling ber use not this number highlight average with
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.
对中序遍历的操作:
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class BSTIterator {
private TreeNode cur;
private Stack<TreeNode> stack = new Stack<TreeNode>();
public BSTIterator(TreeNode root) {
cur = root;
}
/** @return whether we have a next smallest number */
public boolean hasNext() {
return (cur != null || !stack.isEmpty());
}
/** @return the next smallest number */
public int next() {
while (cur != null) {
stack.push(cur);
cur = cur.left;
}
cur = stack.pop();
TreeNode node = cur;
cur = cur.right;
return node.val;
}
}
注意: return (cur != null || !stack.isEmpty());
root 先不push进去,为了next()方便
173.Binary search tree iterator
标签：calling ber use not this number highlight average with
原文地址：http://www.cnblogs.com/apanda009/p/7240006.html
