1361. Validate Binary Tree Nodes

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class Solution {
    public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
        int[] inDegrees = new int[n];
        for (int i = 0; i < n; i++) {
            int from = i;
            int left = leftChild[i], right = rightChild[i];
            if (left != -1 && ++inDegrees[left] > 1) {
                return false;
            }
            if (right != -1 && ++inDegrees[right] > 1) {
                return false;
            }
        }

        Queue<Integer> queue = new LinkedList<>();
        for (int i = 0; i < n; i++) {
            if (inDegrees[i] == 0) {
                queue.offer(i);
            }
        }
        if (queue.size() != 1) {
            return false;
        }

        int nodeCount = 0;
        while (!queue.isEmpty()) {
            int node = queue.poll();
            nodeCount++;
            int left = leftChild[node];
            if (left != -1) {
                queue.offer(left);
            }
            int right = rightChild[node];
            if (right != -1) {
                queue.offer(right);
            }
        }

        return nodeCount == n;
    }
}

References

1361. Validate Binary Tree Nodes