CF1842H Tenzing and Random Real Numbers

There are $ n $ uniform random real variables between 0 and 1, inclusive, which are denoted as $ x_1, x_2, \ldots, x_n $ . Tenzing has $ m $ conditions. Each condition has the form of $ x_i+x_j\le 1 $ or $ x_i+x_j\ge 1 $ . Tenzing wants to know the probability that all the conditions are satisfied, modulo $ 998~244~353 $ . Formally, let $ M = 998~244~353 $ . It can be shown that the answer can be expressed as an irreducible fraction $ \frac{p}{q} $ , where $ p $ and $ q $ are integers and $ q \not \equiv 0 \pmod{M} $ . Output the integer equal to $ p \cdot q^{-1} \bmod M $ . In other words, output the integer $ x $ that $ 0 \le x < M $ and $ x \cdot q \equiv p \pmod{M} $ .

N/A

N/A

In the first test case, the conditions are $ x_1+x_2 \le 1 $ and $ x_3+x_3\ge 1 $ , and the probability that each condition is satisfied is $ \frac 12 $ , so the probability that they are both satisfied is $ \frac 12\cdot \frac 12=\frac 14 $ , modulo $ 998~244~353 $ is equal to $ 748683265 $ . In the second test case, the answer is $ \frac 14 $ . In the third test case, the answer is $ \frac 1{16} $ . In the fourth test case, the sum of all variables must equal $ 2 $ , so the probability is $ 0 $ .