#P2791. Basketball Performance Failure Degree
Basketball Performance Failure Degree
Basketball Performance Failure Degree
There are N special basketballs on the court, among which exactly M are deflated. Thanks to the spectacular skills of Cai Xukun, when he throws a deflated ball it always goes in, and when he throws a ball in normal condition it always misses.
Cai Xukun hosts S tour performances. In the i-th performance, the audience specifies a number ki indicating how many balls will be thrown. Then, from the N basketballs, exactly ni balls are chosen and placed on the court such that exactly mi of them are deflated. Cai Xukun then randomly (uniformly and without replacement) selects ki balls from these ni basketballs to shoot. If he scores with x balls (note that a ball scores if and only if it is deflated), the failure degree of that performance is defined as
$$x^L$$
The performances are mutually independent. The audience wants to know the sum of the expected failure degrees of the S performances, modulo 998244353.
The expected failure degree for one performance is computed by the hypergeometric distribution. In the i-th performance, let the probability of scoring exactly x baskets be
$$P(x)=\frac{\binom{m_i}{x}\,\binom{n_i-m_i}{k_i-x}}{\binom{n_i}{k_i}}.$$
Then the expected failure degree is
$$E_i=\sum_{x=0}^{\min\{k_i,\;m_i\}} x^L \cdot P(x).$$
You are to compute the value
$$\sum_{i=1}^{S} E_i \bmod 998244353.$$
inputFormat
The first line contains four integers N
, M
, L
and S
:
N
(total number of basketballs),M
(number of deflated balls among them),L
(the exponent in the failure degree formula),S
(number of performances).
Then S
lines follow. The i-th of these lines contains three integers ki
, ni
and mi
, which denote that in the i-th performance:
ni
balls are chosen out of theN
basketballs, among which exactlymi
are deflated,- Cai Xukun will then randomly choose
ki
balls to shoot.
You can assume that 0 ≤ mi ≤ ni ≤ N and 0 ≤ ki ≤ ni.
outputFormat
Output a single integer: the sum of the expected failure degrees for all performances, modulo 998244353.
sample
5 3 2 3
2 3 1
3 5 3
1 2 1
665968546
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