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company/google/BinarySearchTreeIterator.java
53 строки
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Kevin Naughton Jr
finish renaming files and directories
27 мар 2018, 19:52
27 мар 2018, 19:52
ec6dfb5
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// 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. /** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class BinarySearchTreeIterator { Stack<TreeNode> stack; public BSTIterator(TreeNode root) { stack = new Stack<TreeNode>(); while(root != null) { stack.push(root); root = root.left; } } /** @return whether we have a next smallest number */ public boolean hasNext() { return stack.isEmpty() ? false : true; } /** @return the next smallest number */ public int next() { TreeNode nextSmallest = stack.pop(); TreeNode addToStack = nextSmallest.right; while(addToStack != null) { stack.add(addToStack); addToStack = addToStack.left; } return nextSmallest.val; } } /** * Your BSTIterator will be called like this: * BSTIterator i = new BSTIterator(root); * while (i.hasNext()) v[f()] = i.next(); */