MOON2 - Moon Safari (Hard)
Air is a music duo from France. You will be told the secret of the critically acclaimed album Moon Safari: mathematics. The goal of your new task is to compute an ethereal sum.
Three trips on the moon are provided, Moon (easy), Moon1 (medium), Moon2 (hard) with different constraints.
Input
The first line contains an integer T, the number of test cases. On the next T lines, you will be given three integers N, a and r.
Output
Output T lines, one for each test case, with SN,a,r = sum( a^i i^r, for i in [1..N] ). Since the answer can get very big, output it modulo 109+7.
Example
Input: 2 3 4 5 6 7 8 Output: 16068 329990641
Explanation
The first case is, with N=3, a=4, r=5, about the sum : 4^1 × 1^5 + 4^2 × 2^5 + 4^3 × 3^5 = 4 + 512 + 15552 = 16068. The second case is, with N=6, a=7, r=8, about the sum : 7^1 × 1^8 + 7^2 × 2^8 + 7^3 × 3^8 + 7^4 × 4^8 + 7^5 × 5^8 + 7^6 × 6^8 + 7^7 × 7^8 = 204329992069 ≡ 329990641 (mod 10^9+7).
Constraints
0 < T×r < 2 560 000 1 < N < 10^9 1 < a < 10^9
Uniform random input in the range. More precise information : there are 5 input files. In0 : T<20000 and r <= 128 In1 : T<2000 and r <= 1250 In2 : T<200 and r <= 11000 In3 : T<20 and r <= 100000 In4 : T<2 and r <= 1000000
Information
This trip can be done with a O(T×r×log(N)) method and some interpreted languages. Edited(2017-02-11, after compiler changes). My non optimal Py3 code got AC under 5s for each of the 5 input files. @speed addicts : My fastest C code got AC in 0.42s. (approx 0.08s per file) Good luck and have fun ;-)
hide comments
jas.py:
2022-10-08 00:10:41
Can a acceptable solution have O(r^2) precomputation (considering file In4)? |
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pranav_arora:
2015-07-21 04:00:05
Can you please give some hints? I have been trying this problem from days but cannot improve the recurrence I set up for the medium version. :(
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Min_25:
2014-10-24 12:18:37
Finally done. :)
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Francky:
2014-06-12 22:18:03
Congratulations to Robert Gerbicz as the first solver. Well done.
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Added by: | Francky |
Date: | 2014-06-07 |
Time limit: | 9s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: ASM64 |
Resource: | Own problem |