All Tracks Problem

Little Shino and Elo Ratings



HackerEarth hired Little Shino to work on the rating system. HackerEarth uses Elo-rating system is used to rank contestants. Suppose two contestants with the current ratings $$r(1)$$ and $$r(2)$$ compete in a contest. Little Shino have to find their updated rating $$r'(1)$$ and $$r'(2)$$ after contest?

Little Shino wrote the algorithm to compute the updated rating but he is busy with other things right now so he asked you to write the sql query.

The algorithm is as follows:

The first step is to compute the transformed rating for each player or team:

$$R(1) = 10^{r(1)/400}$$

$$R(2) = 10^{r(2)/400}$$

In the second step we calculate the expected score for each player:

$$E(1) = \frac {R(1)} {R(1) + R(2)}$$

$$E(2) = \frac {R(2)} {R(1) + R(2)}$$

Now we wait for the match to finish and set the actual score in the third step:

if first contestant's rank is less than second contestant's rank
    S(1) = 1
    S(1) = 0
if second contestant's rank is less than first contestant's rank
    S(2) = 1
    S(2) = 0

Now we can put it all together and in a fourth step find out the updated Elo-rating for each contestant:

$$r'(1) = r(1) + 32 * (S(1) – E(1))$$

$$r'(2) = r(2) + 32 * (S(2) – E(2))$$

This will give the updated ratings of only 2 contestants. If there are more than 2 contestants, you have to calculate the updated ratings for all possible pairs and the final updated rating of a contestant will be the average of all the updated ratings of that contestant .

Note: Output should contain the data in non-increasing order of their updated ratings. The new ratings will be floating point number so round off the answer till the decimal point and print the integer value.

Input Format:

Table : Ratings

Field Type
Name text
Rating int

Table: Rank

Field Type
Name int
Rank int

Output Format:

Field Type
Name text
NewRating text

Sample Input:

Sample Ratings Table:

Name Rating
tourist 3580
Petr 3481

Sample Rank Table:

Name Rank
tourist 2
Petr 1

Sample Output:

Name NewRating
tourist 3560
Petr 3501
Time Limit: 5 sec(s) for each input file.
Memory Limit: 256 MB
Source Limit: 1024 KB
Marking Scheme: Marks are awarded when all the testcases pass.
Allowed Languages: MySQL, PostgreSQL, MSSQL, Oracle Database


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