Leetcode #339. Nested List Weight Sum

[yokostan]

class Solution {
    public int depthSum(List<NestedInteger> nestedList) {
        if (nestedList == null) return 0;
        int sum = 0;
        int level = 1;

        Queue<NestedInteger> queue = new LinkedList<NestedInteger>(nestedList);
        while (!queue.isEmpty()) {
            int size = queue.size();
            for (int i = 0; i < size; i++) {
                NestedInteger ni = queue.poll();
                if (ni.isInteger()) {
                    sum += ni.getInteger() * level;
                }
                else {
                    queue.addAll(ni.getList());
                }
            }
            level++;
        }

        return sum;

    }
}