ABA12D - Sum of divisors!
Note: If you really want to learn something by solving this problem, don't hard code! There is a nice logic behind this!
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Kartheeswaran was recently reading an article on perfect numbers, whose sum of divisors equals twice the number. He was intrigued by them and decided to generate them but to his disappointment they turned out to be quite rare. So he decided to look out for a different property related to sum of divisors. What is more interesting than a number being a prime? So he decided to look out for numbers whose sum of divisors is a prime number and he was the inventor of these special numbers he gave them the name K-numbers.
Given a range [A, B] you are expected to find the number of K-numbers in this range.
Input
The first line of input indicates the number of test cases T. Then in the following T lines there will be a pair of integers A and B.
Output
Output T lines each containing a single integer ācā which denotes the number of K-numbers which lie in the interval [A, B] inclusive of the end points.
Constraints
1 <= T <= 10000
1<=A<=B<=10^6
Example
Input: 2 1 5 9 10 Output: 2 1
Explanation of Sample
1) In the range [1, 5] the K-numbers are 2 and 4 because divisors of 2 are 1 and 2 which sum up to 3, which is a prime. Divisors of 4 are 1, 2 and 4 which sum up to 7, which is a prime.
2) The only K-number in the range [9, 10] is 9.
hide comments
lovecode:
2015-01-18 06:27:05
a very nice question |
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[Lakshman]:
2014-12-24 08:53:16
@Jayadev Rajan No problem with judge. I submitted my code and got AC. Check your algorithm. |
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Jayadev Rajan:
2014-12-24 06:09:48
I feel there is some problem in the way this problem is judged. I tried a Java program which got TLE, but a similar C++ program got AC. The java program was highly optimized to run at .1 sec in the worst case.
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Lehar:
2014-12-22 15:07:48
I got AC with the help of OEIS. If someone is willing to share the logic behind this, please mail me at no.sharing@cheating.com
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उत्कर्ष:
2014-12-21 21:45:05
amazing question! |
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LUCIFER:
2014-12-17 11:11:04
please tell the test case for which answer is wrong for id number 13190802. |
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[Lakshman]:
2014-12-05 09:51:25
@sai sushanth YES. You can use aany thing you want. |
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sai sushanth:
2014-12-05 09:45:06
can we use math.h or not
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DHRUV SHARMA:
2014-11-30 14:41:05
@admin my code is perfectly fine and is working under the time limit on ideone for the worst case but it is giving tle here kindly look into the issue . |
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Varad Raut:
2014-10-23 13:41:04
100th Classical!
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Added by: | Kashyap Krishnakumar |
Date: | 2012-01-13 |
Time limit: | 0.103s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: ASM32-GCC ASM64 MAWK BC C-CLANG NCSHARP CPP14 CPP14-CLANG COBOL COFFEE D-CLANG D-DMD DART ELIXIR FANTOM FORTH GOSU GRV JS-MONKEY JULIA KTLN NIM NODEJS OBJC OBJC-CLANG OCT PICO PROLOG PYPY PYPY3 PY_NBC R RACKET RUST CHICKEN SQLITE SWIFT UNLAMBDA VB.NET |
Resource: | Own problem |