LeetCode 2538: Difference Between Maximum and Minimum Price Sum Solution

class Solution {
    int[] maxSum;
    int[] minSum;
    int[] price;
    List<List<Integer>> adjList;
    int answer;

    public int maxCost(int n, int[][] edges, int[] prices) {
        maxSum = new int[n];
        minSum = new int[n];
        price = prices;
        adjList = new ArrayList<>();
        answer = 0;

        for (int i = 0; i < n; i++) {
            adjList.add(new ArrayList<>());
        }

        for (int[] edge : edges) {
            adjList.get(edge[0]).add(edge[1]);
            adjList.get(edge[1]).add(edge[0]);
        }

        dfs(0, -1);

        return answer;
    }

    private void dfs(int node, int parent) {
        maxSum[node] = price[node];
        minSum[node] = price[node];
        int maxChild = Integer.MIN_VALUE;
        int minChild = Integer.MAX_VALUE;

        for (int child : adjList.get(node)) {
            if (child == parent) continue;
            dfs(child, node);
            maxSum[node] = Math.max(maxSum[node], maxSum[child]);
            minSum[node] = Math.min(minSum[node], minSum[child]);
            maxChild = Math.max(maxChild, maxSum[child]);
            minChild = Math.min(minChild, minSum[child]);
        }

        answer = Math.max(answer, Math.max(Math.abs(maxSum[node] - minChild), Math.abs(maxChild - minSum[node])));
    }
}