Codeforces Round 800 (Div. 1)

Solutions for Codeforces Round 800 (Div. 1) (contest 1693). 1/6 problems verified against sample I/O. Difficulty range: 1300-3400.

6 items

Codeforces Round 800 (Div. 1)

Type: Div. 1 | Problems: 6 | Verified: 1/6 | Rating range: 1300-3400 | Time: 19m 59s

Problem Name Rating Tags Solve Time Verified
A Directional Increase 1300 greedy 2m 30s ✗
B Fake Plastic Trees 1700 dfs-and-similar, dp, greedy 2m 26s ✓
C Keshi in Search of AmShZ 2300 graphs, greedy, shortest-paths 2m 18s ✗
D Decinc Dividing 2800 brute-force, data-structures, divide-and-conquer 2m 27s ✗
E Outermost Maximums 3400 data-structures, greedy 2m 38s ✗
F I Might Be Wrong 3400 binary-search, greedy, two-pointers 7m 40s ✗
Practice › Codeforces Solutions › Codeforces Round 800 (Div. 1) ›

CF 1693F - I Might Be Wrong

The problem gives a binary string consisting of 0s and 1s, and you are allowed to perform a sorting operation on any contiguous substring.
codeforces competitive-programming binary-search greedy two-pointers Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 800 (Div. 1) ›

CF 1693E - Outermost Maximums

We are given an array of length $n+2$, where the first and last elements are fixed at zero, and the middle $n$ elements are arbitrary non-negative integers.
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CF 1693D - Decinc Dividing

We are given a permutation of numbers from 1 to $n$, and we are asked to count the number of contiguous subarrays that are "Decinc." A subarray is Decinc if we can remove some decreasing subsequence (possibly empty) so that the remaining elements are strictly increasing.
codeforces competitive-programming brute-force data-structures divide-and-conquer dp greedy Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 800 (Div. 1) ›

CF 1693A - Directional Increase

The proposed solution answers the exercise that was actually asked. Exercise 3.4.2.10 asks for a modification of Algorithm R that eliminates the reservoir when the current sample of size $n$ can be stored directly in memory.
codeforces competitive-programming greedy Jun 9, 2026
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CF 1693B - Fake Plastic Trees

We are given a rooted tree. Every vertex starts with value 0, and each vertex v has a required interval [lv, rv]. An operation chooses some root-to-vertex path and adds values along that path.
codeforces competitive-programming dfs-and-similar dp greedy trees Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 800 (Div. 1) ›

CF 1693C - Keshi in Search of AmShZ

We are given a directed graph representing cities in Italy connected by roads. Keshi starts in city 1 and wants to reach city n, where AmShZ is waiting. Each day, AmShZ can either mark a single road as blocked or instruct Keshi to move.
codeforces competitive-programming graphs greedy shortest-paths Jun 9, 2026