thinking：

（1）每次選擇輸出的數字是當前序列中最小的，記該數字下標為 index，數字為a

（2）檢查index 之後的最小數為b

(3)如果index之前有小於b且大於a的數字出現，說明這些數字是亂序的數字，要和a一行保序輸出

• 此處用 優先佇列會更有優勢！！！

int output_in_order(vector<int>  &unordered_sequence)
{
	int next_output = 1，got_output;

	priority_queue<int, vector<int>, greater<int> > pq;

	for(int i = 0; i < unordered_sequence.size(); i++)
	{
		pq.push(unordered_sequence[i]);

		if(pq.top() < next_output)
		{
			cout << "duplicated index or index <= 0 in the sequence" << endl;
			return -1;
		}
		
		got_output= 0;
		if(!pq.empty()  && pq.top() == next_output)
		{
			if(got_output)
				cout << ", ";
			cout << next_output;
			next_output++;
			pq.pop();
			got_output = 1;
		}
		if(got_output)
			cout << endl;
	}
	if(pq.empty())
		return 0;
	cout << "missing some index in the sequence" << endl;
	return -2;
}