CF283A.Cows and Sequence
普及/提高-
通过率:0%
AC君温馨提醒
该题目为【codeforces】题库的题目,您提交的代码将被提交至codeforces进行远程评测,并由ACGO抓取测评结果后进行展示。由于远程测评的测评机由其他平台提供,我们无法保证该服务的稳定性,若提交后无反应,请等待一段时间后再进行重试。
题目描述
Bessie and the cows are playing with sequences and need your help. They start with a sequence, initially containing just the number 0, and perform n operations. Each operation is one of the following:
- Add the integer xi to the first ai elements of the sequence.
- Append an integer ki to the end of the sequence. (And hence the size of the sequence increases by 1)
- Remove the last element of the sequence. So, the size of the sequence decreases by one. Note, that this operation can only be done if there are at least two elements in the sequence.
After each operation, the cows would like to know the average of all the numbers in the sequence. Help them!
输入格式
The first line contains a single integer n (1<=n<=2⋅105) — the number of operations. The next n lines describe the operations. Each line will start with an integer ti (1<=ti<=3) , denoting the type of the operation (see above). If ti=1 , it will be followed by two integers ai,xi (∣xi∣<=103; 1<=ai) . If ti=2 , it will be followed by a single integer ki (∣ki∣<=103) . If ti=3 , it will not be followed by anything.
It is guaranteed that all operations are correct (don't touch nonexistent elements) and that there will always be at least one element in the sequence.
输出格式
Output n lines each containing the average of the numbers in the sequence after the corresponding operation.
The answer will be considered correct if its absolute or relative error doesn't exceed 10−6 .
输入输出样例
输入#1
5 2 1 3 2 3 2 1 3
输出#1
0.500000 0.000000 1.500000 1.333333 1.500000
输入#2
6 2 1 1 2 20 2 2 1 2 -3 3 3
输出#2
0.500000 20.500000 14.333333 12.333333 17.500000 17.000000
说明/提示
In the second sample, the sequence becomes