Codeforces Global Round 19

Solutions for Codeforces Global Round 19 (contest 1637). 4/8 problems verified against sample I/O. Difficulty range: 800-3500.

8 items

Codeforces Global Round 19

Type: Global | Problems: 8 | Verified: 4/8 | Rating range: 800-3500 | Time: 14m 35s

Problem Name Rating Tags Solve Time Verified
A Sorting Parts 800 brute-force, sortings 1m 23s ✓
B MEX and Array 1100 brute-force, dp, greedy 1m 32s ✓
C Andrew and Stones 1200 greedy, implementation 1m 37s ✓
D Yet Another Minimization Problem 1800 dp, greedy, math 1m 31s ✓
E Best Pair 2100 binary-search, brute-force, implementation 2m 38s ✗
F Towers 2500 constructive-algorithms, dfs-and-similar, dp 2m 25s ✗
G Birthday 3000 constructive-algorithms, greedy, math 1m 52s ✗
H Minimize Inversions Number 3500 data-structures, greedy, math 1m 37s ✗
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CF 1637H - Minimize Inversions Number

We are given a permutation, meaning every number from 1 to n appears exactly once in some order. We are allowed to pick some subsequence of this array, remove those chosen elements, and then reinsert them as a block at the very front, preserving their relative order.
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CF 1637G - Birthday

We are given the numbers from $1$ to $n$ for each test case, and we can repeatedly pick any two numbers $x$ and $y$, remove them, and add two numbers: $x+y$ and $ The input size allows $n$ up to $5 cdot 10^4$ per test case, with a total sum of $n$ over all test cases also…
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CF 1637E - Best Pair

This problem is rated 3500 and its solution relies on a fairly deep structural characterization of graphs whose cycle space admits a consistent cyclic orientation.
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CF 1637F - Towers

We are working on a tree where each vertex has a height value. The task is to place a set of “towers” on vertices, and assign each tower a positive integer efficiency.
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CF 1637D - Yet Another Minimization Problem

We have two arrays of equal length. For every position, we may either keep the pair as it is or swap the two numbers inside that position. After deciding this independently for all indices, both arrays acquire new values.
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CF 1637C - Andrew and Stones

We are given a line of piles, each pile containing some number of stones. The only allowed operation removes two stones from some middle pile and redistributes them as one stone to a pile on its left and one stone to a pile on its right.
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CF 1637B - MEX and Array

We are given an array of integers and asked to compute a sum of “values” over all its subsegments. A subsegment is any contiguous slice of the array. The value of a subsegment is defined as the maximum cost of any partition of that subsegment.
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CF 1637A - Sorting Parts

We have an array and we are forced to perform exactly one operation. We choose a position that splits the array into two non-empty parts. Then we sort the left part and the right part independently.
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