Beautiful numbers

3.7

13 votes
Algorithms, Basics of Greedy Algorithms, Greedy Algorithms
Problem

Any number is called beautiful if it consists of $$2N$$ digits and the sum of the first $$N$$ digits is equal to the sum of the last $$N$$ digits. Your task is to find the count of beautiful numbers in the interval from $$L$$ to $$R$$ (including $$L$$ and $$R$$).

Beautiful numbers do not have leading zeroes.

Input format

  • The first line contains an integer $$T$$ denoting the number of test cases.
  • The first line of each test case contains two space-separated integers $$L$$ and $$R$$ denoting the range interval \([L,R]\).

Output format

For each test case, print the count of beautiful numbers in a new line.

Constraints

\(1 \le T \le 200000\\ 1 \le L \le R \le 1000000000\)

Time Limit: 2
Memory Limit: 256
Source Limit:
Explanation

There are only $$9$$ beautiful numbers in the first $$100$$ integers. \(11,22,33,44,55,66,77,88\) and $$99$$ are the beautiful numbers in the range \([1,100]\).

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