从零开始Leetcode – Day 18
Binary Search Tree Iterator
https://leetcode.com/problems/binary-search-tree-iterator/
- 这里是用stack 来实习左中右， inorder 遍历。
- 实现stack, push和pop， LIFO
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* Definition for binary tree
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
var stack =[];
* @constructor
* @param {TreeNode} root - root of the binary search tree
*/
var BSTIterator = function(root) {
while(root !== null){
stack.push(root);
root = root.left;
}
};
* @this BSTIterator
* @returns {boolean} - whether we have a next smallest number
*/
BSTIterator.prototype.hasNext = function() {
return (stack.length > 0) ? true : false;
};
* @this BSTIterator
* @returns {number} - the next smallest number
*/
BSTIterator.prototype.next = function() {
var node = stack.pop();
var res = node.val;
if(node.right !== null){
node = node.right;
while(node !== null){
stack.push(node);
node = node.left;
}
}
return res;
};
* Your BSTIterator will be called like this:
* var i = new BSTIterator(root), a = [];
* while (i.hasNext()) a.push(i.next());
*/
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