a permutation is valid only if |ai — i| != k for all 1<=i<=n. Count the number of valid permutations.
Constraints: 2 ≤ N ≤ 2000
1 ≤ K ≤ N − 1
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Among permutations of length N, how many satisfy |a_i − i| ≠ K
Revision en6, by elizabeth_zou_fanboi, 2024-11-09 21:03:06
History
Revisions
| Rev. | Lang. | By | When | Δ | Comment | |
|---|---|---|---|---|---|---|
| en7 |
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elizabeth_zou_fanboi | 2024-11-09 21:04:04 | 2783 | Reverted to en5 | |
| en6 |
|
elizabeth_zou_fanboi | 2024-11-09 21:03:06 | 2783 | Reverted to en4 | |
| en5 |
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elizabeth_zou_fanboi | 2024-11-09 21:00:28 | 2783 | ||
| en4 |
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elizabeth_zou_fanboi | 2024-11-08 20:51:00 | 112 | ||
| en3 |
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elizabeth_zou_fanboi | 2024-11-08 20:02:58 | 4 | Tiny change: 'N ≤ 2000\n1 ≤ K ≤ ' -> 'N ≤ 2000\n\n\n1 ≤ K ≤ ' (published) | |
| en2 |
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elizabeth_zou_fanboi | 2024-11-08 20:02:30 | 4 | Tiny change: '− i| ≠ K\nConstrai' -> '− i| ≠ K\n\n\nConstrai' (saved to drafts) | |
| en1 |
|
elizabeth_zou_fanboi | 2024-11-08 20:02:12 | 174 | Initial revision (published) |
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