Black Box
Time Limit: 1000MS |
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Memory Limit: 10000K |
Total Submissions: 10378 |
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Accepted: 4276 |
Description
Our Black Box represents a primitive database. It can save an integer array and has a special i variable. At the initial moment Black Box is empty and i equals 0. This Black Box processes a sequence of commands (transactions). There are two types of transactions:
ADD (x): put element x into Black Box;
GET: increase i by 1 and give an i-minimum out of all integers containing in the Black Box. Keep in mind that i-minimum is a number located at i-th place after Black Box elements sorting by non- descending.
Let us examine a possible sequence of 11 transactions:
Example 1
N Transaction i Black Box contents after transaction Answer
(elements are arranged by non-descending)
1 ADD(3) 0 3
2 GET 1 3 3
3 ADD(1) 1 1, 3
4 GET 2 1, 3 3
5 ADD(-4) 2 -4, 1, 3
6 ADD(2) 2 -4, 1, 2, 3
7 ADD(8) 2 -4, 1, 2, 3, 8
8 ADD(-1000) 2 -1000, -4, 1, 2, 3, 8
9 GET 3 -1000, -4, 1, 2, 3, 8 1
10 GET 4 -1000, -4, 1, 2, 3, 8 2
11 ADD(2) 4 -1000, -4, 1, 2, 2, 3, 8
It is required to work out an efficient algorithm which treats a given sequence of transactions. The maximum number of ADD and GET transactions: 30000 of each type.
Let us describe the sequence of transactions by two integer arrays:
1. A(1), A(2), ..., A(M): a sequence of elements which are being included into Black Box. A values are integers not exceeding 2 000 000 000 by their absolute value, M <= 30000. For the Example we have A=(3, 1, -4, 2, 8, -1000, 2).
2. u(1), u(2), ..., u(N): a sequence setting a number of elements which are being included into Black Box at the moment of first, second, ... and N-transaction GET. For the Example we have u=(1, 2, 6, 6).
The Black Box algorithm supposes that natural number sequence u(1), u(2), ..., u(N) is sorted in non-descending order, N <= M and for each p (1 <= p <= N) an inequality p <= u(p) <= M is valid. It follows from the fact that for the p-element of our u sequence we perform a GET transaction giving p-minimum number from our A(1), A(2), ..., A(u(p)) sequence.
Input
Input contains (in given order): M, N, A(1), A(2), ..., A(M), u(1), u(2), ..., u(N). All numbers are divided by spaces and (or) carriage return characters.
Output
Write to the output Black Box answers sequence for a given sequence of transactions, one number each line.
Sample Input
7 4
3 1 -4 2 8 -1000 2
1 2 6 6
Sample Output
3
3
1
2
这个题的大意就是给你两个数列我们用a,b表示,第一个数列表示你要加入黑盒的值,然后第二个数列表示在插入b[i]个数时,第i小的数是几,比如说示例上:
第一个数是1也就是插入一个数(3)时,第i(1)小的数是3.
第二个数是2也就是插入两个数(3,1)时第i(2)小的数是3.
第三个数是6也就是插入六个数(3,1,-4,2,8,-1000)第i(3)小的数是1.
然后就是想一想怎么做。单纯输出第几大可能不难,但这是实时更新的数列,所以我们用优先队列来更新我们的动态数组,但光用一个肯定是不行的,因为优先队列输出头顶元素好用,每次重复压入,出列,肯定是吃不消的。这里我们可以考虑用两个优先队列,来把这个动态的数组分割开,用一个优先队列来存储前i小的数,它不是要求每次输出第i个小的数么,我们暂且称之为in队列,表示前i小的数,这样我们把一个q队列分割成两个,in表示前i小的数,out表示后面大的数,那么,我们每次只需要输出out的顶元素就可以了,输出之后把out的顶元素压入in队列中。在压入之前我们要考虑确保in队列中的每个元素都是比out队列中元素要小的,不然肯定是错的。
利用in队列的最大值比out队列中的最小值小,便可以确保in队列中的每个值都比out队列中的全部的值要小了。
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