can someone explain how to do this problem http://codeforces.me/contest/134/problem/B
i used dfs that resulted in TLE, number theory tag is given at hints, but i am not able to understand how to do it ?
| № | Пользователь | Рейтинг |
|---|---|---|
| 1 | Benq | 3676 |
| 2 | Kevin114514 | 3659 |
| 3 | jiangly | 3640 |
| 4 | turmax | 3450 |
| 5 | tourist | 3408 |
| 6 | strapple | 3360 |
| 7 | Um_nik | 3354 |
| 8 | squareOf105 | 3348 |
| 9 | maroonrk | 3312 |
| 10 | idontwannadothis…e | 3191 |
| Страны | Города | Организации | Всё → |
| № | Пользователь | Вклад |
|---|---|---|
| 1 | Qingyu | 155 |
| 2 | nik_exists | 151 |
| 3 | maspy | 149 |
| 4 | AmShZ | 145 |
| 5 | Um_nik | 143 |
| 6 | Errichto | 139 |
| 7 | BledDest | 136 |
| 8 | adamant | 135 |
| 9 | maroonrk | 132 |
| 10 | cry | 130 |
read about Euclidean algorithm.
when you go forward, from any vertex (a, b) you can go into 2 other vertices: (a, a + b) or (a + b, b), but when you go backward at any step there is only one vertex to move in: (a, b - a) if b > a, or (a - b, b) if a > b
so, solution is simple bruteforce, and it works fast.