2265. Count Nodes Equal to Average of Subtree 

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class Solution {
    public int averageOfSubtree(TreeNode root) {
        return dfs(root)[2];
    }

    private int[] dfs(TreeNode root) {
        int[] res = new int[3]; // (subNodeSum, subNodeCount, averageNodeCount)

        if (root == null) {
            return res;
        }

        int[] left = dfs(root.left);
        int[] right = dfs(root.right);

        int nodeSum = left[0] + right[0] + root.val;
        int nodeCount = left[1] + right[1] + 1;
        if (nodeSum / nodeCount == root.val) {
            res[2] += 1;
        }
        res[0] = nodeSum;
        res[1] = nodeCount;
        res[2] += left[2] + right[2];
        
        return res;
    }
}

注意节点平均值的计算题目要求直接使用除法，除不尽的部分直接丢弃。

References

2265. Count Nodes Equal to Average of Subtree