| № | Пользователь | Рейтинг |
|---|---|---|
| 1 | ecnerwala | 3649 |
| 2 | Benq | 3581 |
| 3 | orzdevinwang | 3570 |
| 4 | Geothermal | 3569 |
| 4 | cnnfls_csy | 3569 |
| 6 | tourist | 3565 |
| 7 | maroonrk | 3531 |
| 8 | Radewoosh | 3521 |
| 9 | Um_nik | 3482 |
| 10 | jiangly | 3468 |
| Страны | Города | Организации | Всё → |
| № | Пользователь | Вклад |
|---|---|---|
| 1 | maomao90 | 174 |
| 2 | awoo | 164 |
| 3 | adamant | 162 |
| 4 | TheScrasse | 159 |
| 5 | nor | 158 |
| 6 | maroonrk | 156 |
| 7 | -is-this-fft- | 151 |
| 8 | SecondThread | 147 |
| 9 | orz | 146 |
| 10 | pajenegod | 145 |
Hi, Codeforces. I've recently found an interesting problem:
Given an undirected tree with n vertices. Find out how many different ways you can orient the edges of the tree so that the result graph will contain exactly m vertices with zero outdegree modulo 109 + 7, (1 ≤ n ≤ 1000, 0 ≤ m ≤ n).
Could someone help me with this problem and explain the solution?
dp[v][cnt][flag] is the number of ways to make cnt vertices with zero outdegree in the subtree of v, and flag is 1 if the vertex v have a zero outdegree else it is 0 (so n * m * 2 memory)
to recalc this dp you just go with dfs and then you do knapsack-like solution like in this task 815C