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| class Solution {
public int numColor(TreeNode root) {
Set<Integer> colors = new HashSet<>();
dfs(colors, root);
return colors.size();
}
private void dfs(Set<Integer> colors, TreeNode root) {
if (root == null) {
return;
}
colors.add(root.val);
dfs(colors, root.left);
dfs(colors, root.right);
}
}
|