Codeforces Round 625 (Div. 1, based on Technocup 2020 Final Round)
3 problems from Codeforces Round 625 (Div. 1, based on Technocup 2020 Final Round) (contest 1320), difficulty 1700-2500. 1/3 solutions verified against sample I/O.
Codeforces Round 625 (Div. 1, based on Technocup 2020 Final Round)
Div. 1 | 3 problems | 1/3 verified | Difficulty 1700-2500 | 10m 5s
| # | Problem | Rating | Tags | Accepted | Time | ✓ |
|---|---|---|---|---|---|---|
| B | Navigation System | 1700 | dfs-and-similar, graphs, shortest-paths | 6,437 | 2m 48s | ✓ |
| C | World of Darkraft: Battle for Azathoth | 2000 | brute-force, data-structures, sortings | 3,426 | 2m 48s | |
| D | Reachable Strings | 2500 | data-structures, hashing, strings | 1,692 | 4m 29s |
CF 1320D - Reachable Strings
We are given a fixed binary string, and we repeatedly consider two kinds of local transformations on any contiguous segment of length three: swapping 011 into 110, or the reverse swap 110 into 011.
CF 1320B - Navigation System
We are given a directed graph where intersections are nodes and roads are one-way edges. We also know a fixed simple route Polycarp actually drives from his home to his work.
CF 1320C - World of Darkraft: Battle for Azathoth
Yes, the inequality $nu(n) le 2^{l(n) - lambda(n)}$ holds for all positive integers $n$. Consider an addition chain of minimal length $l(n)$ and let $lambda(n)$ be the length of a shortest chain consisting only of doubling steps.