11

2017.9.8

中序遍历二叉查找树，那么key就是有序的。

依次进行比较即可。

/** * Definition of TreeNode: * public class TreeNode { *     public int val; *     public TreeNode left, right; *     public TreeNode(int val) { *         this.val = val; *         this.left = this.right = null; *     } * } */public class Solution {    /*     * @param root: param root: The root of the binary search tree     * @param k1: An integer     * @param k2: An integer     * @return: return: Return all keys that k1<=key<=k2 in ascending order     */    public List<Integer> searchRange(TreeNode root, int k1, int k2) {        // write your code hereList<Integer> res = new LinkedList<>();LinkedList<TreeNode> stack = new LinkedList<TreeNode>();if(root == null){return null;}while(root != null || !stack.isEmpty()){while(root!= null){stack.push(root);root = root.left;}root = stack.pop();if(root.val >= k1 && root.val <= k2){res.add(root.val);}root = root.right;}return res;    }}