Distinct Colors - Implementation

Here is the distinct colors implementation:

function distinctColors(n, adj, color):
    answer = array of size n
    colorSet = array of n empty sets

    function dfs(u, parent):
        bigChild = -1
        bigSize = 0

        for v in adj[u]:
            if v != parent:
                dfs(v, u)
                if colorSet[v].size > bigSize:
                    bigSize = colorSet[v].size
                    bigChild = v

        // Take largest child's set
        if bigChild != -1:
            swap(colorSet[u], colorSet[bigChild])

        // Merge smaller children
        for v in adj[u]:
            if v != parent and v != bigChild:
                for c in colorSet[v]:
                    colorSet[u].add(c)

        // Add current node's color
        colorSet[u].add(color[u])
        answer[u] = colorSet[u].size

    dfs(1, 0)
    return answer

Time: $O(n \log n)$. Space: $O(n)$.