void findNearest(TreeNode root, double target, Deque<TreeNode> s, boolean fromLeft) {
while (root != null) {
s.push(root);
//System.out.printf("fromLeft = %b, push %d\n", fromLeft, root.val);
if (root.val == target) {
break;
}
if (root.val < target) {
root = root.right;
} else {
root = root.left;
}
}
if (fromLeft) {
while (!s.isEmpty() && s.peek().val > target) {
//System.out.printf("pop %d\n", s.peek().val);
s.pop();
}
} else {
while (!s.isEmpty() && s.peek().val < target) {
//System.out.printf("pop %d\n", s.peek().val);
s.pop();
}
}
}
public List<Integer> closestKValues(TreeNode root, double target, int k) {
Deque<TreeNode> leftS = new ArrayDeque<TreeNode>();
Deque<TreeNode> rightS = new ArrayDeque<TreeNode>();
findNearest(root, target, leftS, true);
findNearest(root, target, rightS, false);
List<Integer> res = new ArrayList<Integer>();
while (res.size() < k) {
boolean use_left = false;
boolean use_right = false;
if (leftS.isEmpty()) {
use_right = true;
} else if (rightS.isEmpty()) {
use_left = true;
} else if (leftS.peek().val == rightS.peek().val) {
use_left = use_right = true;
} else if (target - leftS.peek().val < rightS.peek().val - target) {
use_left = true;
} else {
use_right = true;
}
res.add(use_left ? leftS.peek().val : rightS.peek().val);
if (use_left) {
TreeNode node = leftS.pop();
node = node.left;
while (node != null) {
leftS.push(node);
node = node.right;
}
while (!leftS.isEmpty() && leftS.peek().val > target) {
leftS.pop();
}
}
if (use_right) {
TreeNode node = rightS.pop();
node = node.right;
while (node != null) {
rightS.push(node);
node = node.left;
}
while (!rightS.isEmpty() && rightS.peek().val < target) {
rightS.pop();
}
}
}
return res;
}
