统计最高分的节点数目

// 思路：
// 1. 构建孩子列表。
// 2. 使用递归计算每个节点的子树大小。
// 3. 计算每个节点的分数并统计最高分数的节点数。
// 4. 使用 Java Stream API 进行流处理。

import java.util.*;
import java.util.stream.*;

public class TreeHighestScoreStream {
    public int countHighestScoreNodes(int[] parents) {
        int n = parents.length;
        List<List<Integer>> children = IntStream.range(0, n)
                .mapToObj(i -> new ArrayList<Integer>())
                .collect(Collectors.toList());
        for (int i = 1; i < n; i++) {
            children.get(parents[i]).add(i);
        }

        int[] subtreeSize = new int[n];
        dfs(0, children, subtreeSize);

        int[] scores = new int[n];
        IntStream.range(0, n).forEach(i -> {
            int score = 1;
            int totalSize = n - 1;
            for (int child : children.get(i)) {
                score *= subtreeSize[child];
                totalSize -= subtreeSize[child];
            }
            if (i != 0) {
                score *= totalSize;
            }
            scores[i] = score;
        });

        int maxScore = Arrays.stream(scores).max().orElse(0);
        return (int) Arrays.stream(scores).filter(score -> score == maxScore).count();
    }

    private int dfs(int node, List<List<Integer>> children, int[] subtreeSize) {
        int size = 1;
        for (int child : children.get(node)) {
            size += dfs(child, children, subtreeSize);
        }
        subtreeSize[node] = size;
        return size;
    }
}