# Test case [5,1,6,null,3,null,null,2,4]

• I'm not sure what is wrong with my code, the test case is:

``````Submission Result: Wrong Answer
Input:
[5,1,6,null,3,null,null,2,4]
Output:
[[1,2],[5,3],[4,6]]
Expected:
[[1,2],[5,3],[6,4]]
``````

The code is:

``````public List<List<Integer>> verticalOrder(TreeNode root) {
final Map<Integer, List<Integer>> map = new HashMap<>();
solve(root, 0, map);
final List<Integer> sortedKeys = new ArrayList<>(map.keySet());
Collections.sort(sortedKeys);
final List<List<Integer>> result = new ArrayList<>();
for (Integer i: sortedKeys) {
result.add(map.get(i));
}
return result;
}

private void solve(TreeNode root, int seed, Map<Integer, List<Integer>> map) {
if (root == null) {
return;
}
if (!map.containsKey(seed)) {
map.put(seed, new ArrayList<Integer>());
}
map.get(seed).add(root.val);
solve(root.left, seed - 1, map);
solve(root.right, seed + 1, map);
}
``````

I run the above code in my IDE, build the tree regarding the input and have an expected output: [[1, 2], [5, 3], [6, 4]]. The order for 1,2 and 5,3 is right. So, I'm not sure how nodes 4 and 6 could be swapped. Can anyone see the issue in the code?

• exactly same question here. Waiting . . .

• I've met this problem as well, then I changed my code to print nodes from top to bottom and left to right.
In other words, use bfs instead of dfs.

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