Klavir
의견: 0
1 \(s / 64\) \(MB / 160\) points
Young Alisa likes to play the piano using only one finger. Unfortunately, Alisa never learned
to play the piano, so her playing is entirely random. More precisely, any time she chooses a
tone to play, she does it independently of all previous tones, and chooses each of the \(N\)
tones with the same probability.
Her good friend Mirta wants to listen to a composition containing \(M\) consecutive tones, but
since Alisa plays the piano randomly, Mirta does not know how long she will have to wait to
hear an array of exactly these \(M\) tones. Help Mirta determine the expected number of key
presses in order to hear, for the first time, her wanted array of consecutive tones. Moreover,
since Mirta is a very curious girl, she also wants to know the expected number of key
presses for each prefix of her wanted array of tones.
In test cases worth 64 points in total, it will hold 1 ≤ \(M\)
≤ 200.
The first line of input contains the positive integer \(N\)
, the number of different piano tones (1 ≤
\(N\)
≤ 100).
The second line of input contains the positive integer \(M\)
, the length of the wanted array (1 ≤
\(M \le 10\) {6}{ }).
The third line of input contains the array of \(M\)
positive integers between 1 and \(N\)
.
The \(i\)^{th} of the following M lines must contain the expected number of key presses in order for
Mirta to hear the prefix of length \(i\)
of her wanted array of tones, modulo 10 {9}{ } + 7.
The test data will be such that the expected number of key presses will always be an integer.
2
2
1 2
2
2
1 1
3
3
1 2 3output
output
2
4
2
6
3
9
27평가 및 의견
Klavir
Log in to rate problems.
아직 의견이 없습니다. 자격이 된다면 위 양식에서 가장 먼저 평가해 보세요.
풀이 제출
Klavir