Submit | All submissions | Best solutions | Back to list |
FINDPRM - Finding Primes |
One commonly used method to calculate all primes in the range [2 .. n] is to start with the number 2, mark it as prime, and mark all its multiples (excluding itself) as not prime. Then, we find the next smallest unmarked number, mark it as prime, and mark all its multiples (excluding itself) as not prime. Continuing this way, we get a list of all primes.
Now, let us say that we modified the above algorithm, and start with n instead of 2. We mark it as prime, and mark all its factors (excluding itself) as not prime. Then we find the next greatest unmarked number, mark it as prime, and mark all its factors (excluding itself) as not prime. Continuing this way, we get a list of all primes.
Now you wonder, given a value of n, how many numbers are such that both the above algorithms will mark them as prime?
Input
The first line contains T the number of test cases. Each of the next T lines contain an integer n.
Output
Output T lines, one for each test case, containing the required answer.
Example
Input: 3 2 4 7 Output: 1 1 2
Constraints
1 ≤ T ≤ 100000
2 ≤ n ≤ 10000000
Added by: | Varun Jalan |
Date: | 2010-01-24 |
Time limit: | 1s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: PERL6 |
Resource: | own problem used for Codechef Snackdown Onsite |
hide comments
|
||||||
2016-06-24 14:08:54
century completed |
||||||
2016-06-17 17:10:45
cout gives tle and printf accepted ! -_- |
||||||
2016-01-30 11:59:17
Any one can help me understand this input? In case n = 4, it make 4, 5, 6, 7, 9, 11,... are primes, 3 of them are really primes (5, 7, 11) then answer for this case is at least 3. What wrong with me? |
||||||
2015-06-18 20:01:04 kartikay singh
Simple sieve :) No need to optimise |
||||||
2015-05-27 18:04:43 Ashish Sareen
Yes you do need to optimise prime sieve. Got too many TLE's because of that |
||||||
2015-04-23 21:18:11 Vipul Srivastava
no need to optimise the prime sieve.. |
||||||
2015-04-05 11:12:20 Fz
yeah.. finally got AC! the only trick->optimise your sieve! |
||||||
2011-08-23 00:33:23 numerix
@sandeep: It's correct. |
||||||
2011-08-23 00:33:23 sandeep pandey
for n=10000000 my ans:316066 this is correct or not??? |