Submit | All submissions | Best solutions | Back to list |
PRLOVE - Expected Time to Love |
Alice has a problem. She loves Bob but is unable to face up to him. So she decides to send a letter to Bob expressing her feelings. She wants to send it from her computer to Bob's computer through the internet.
The internet consists of N computers, numbered from 1 to N. Alice's computer has the number 1 and Bob's computer has the number N.
Due to some faulty coding, the computers start behaving in unexpected ways. On recieving the file, computer i will forward it to computer j with probability Pij. The time taken to transfer the file from computer i to computer j is Tij.
Find the expected time before Bob finds out about Alice's undying love for him.
Note: Once the letter is recieved by Bob's computer, his computer will just deliver it to Bob and stop forwarding it.
Input
First line contains T, the total test cases.
Each test case looks as follows:
First line contains N, the total number of computers in the network.
The next N lines contain N numbers each. The j'th number on the i'th line is the value Pij in percents.
The next N lines contain N numbers each. The j'th number on the i'th line is the value Tij.
Output
Output a single line with a real number - The expected time of the transfer.
Your output will be considered correct if each number has an absolute or relative error less than 10−6.
Constraints
N≤100
T≤5
For all i, Pi1+Pi2+…+PiN=100
PNN=100
For all i, j, 0≤Tij≤10000
You can safely assume that from every computer, the probability of eventually reaching Bob's computer is greater than 0.
Example
Sample Input: 2 4 0 50 50 0 0 0 0 100 0 0 0 100 0 0 0 100 0 2 10 0 0 0 0 0 0 0 0 0 0 0 0 0 2 99 1 0 100 10 2 0 0 Sample Output: 6.000000 992.000000
Added by: | Aditya |
Date: | 2013-02-03 |
Time limit: | 1s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | BASH C C++ 4.3.2 CPP FORTRAN HASK JAVA PAS-GPC PAS-FPC PYTHON PYTHON3 PY_NBC RUBY SCALA WHITESPACE |
Resource: | ByteCode '13 |
hide comments
2018-05-23 09:10:29 akshay
@thomas underflow... log sum exp trick is your friend ... |
|
2017-12-16 23:55:08 Thomas Dybdahl Ahle
Say you have a chain, where each computer has probability 1% of sending to the next computer, and 99% of sending to the first. Then the message would have to travel more than 100^100 times to get to Bob, in expectation. With the bounds on T, that means the answer can be as large as 10^204. Is that correct? Getting 10^-6 absolute precision on numbers that large is pretty difficult. Last edit: 2017-12-16 23:55:44 |
|
2013-03-08 11:45:04 The Mundane Programmer
Can anyone explain test cases...... |