Given n<=1000000 and k<=n*(n-1)/2 construct a sequence of length n that has exactly k inversions. How do I solve this? Thanks!
# | User | Rating |
---|---|---|
1 | tourist | 4009 |
2 | jiangly | 3821 |
3 | Benq | 3736 |
4 | Radewoosh | 3631 |
5 | jqdai0815 | 3620 |
6 | orzdevinwang | 3529 |
7 | ecnerwala | 3446 |
8 | Um_nik | 3396 |
9 | ksun48 | 3388 |
10 | gamegame | 3386 |
# | User | Contrib. |
---|---|---|
1 | cry | 164 |
1 | maomao90 | 164 |
3 | Um_nik | 163 |
4 | atcoder_official | 161 |
5 | -is-this-fft- | 158 |
6 | awoo | 157 |
7 | adamant | 156 |
8 | TheScrasse | 154 |
8 | nor | 154 |
10 | Dominater069 | 153 |
Given n<=1000000 and k<=n*(n-1)/2 construct a sequence of length n that has exactly k inversions. How do I solve this? Thanks!
Name |
---|
Every number $$$1 \le i \le n$$$ can add maximum $$$n - i$$$ inversions. So we can run from $$$1$$$ to $$$n$$$ and if $$$cnt_{inversion} + (n - i) \le k$$$ then place $$$i$$$ on maximum right unused position and doing $$$cnt_{inversion} += (n - i)$$$. Else place $$$i$$$ on minimal left unused position and $$$cnt_{inversion}$$$ was not changed.
https://ideone.com/kXZNIe