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class Solution {
    public int triangularSum(int[] nums) {
        Deque<Integer> numQ = new ArrayDeque<>();
        for (int num : nums) {
            numQ.offer(num);
        }
        while (numQ.size() > 1) {
            for (int i = numQ.size() - 1; i > 0; i--) {
                int topNum = numQ.poll();
                numQ.offer((topNum + numQ.peekFirst()) % 10);
            }
            numQ.poll();
        }
        return numQ.poll();
    }
}

直接用queue.

时间复杂度: O(n!)
空间复杂度: O(n)