Codeforces Round 917 (Div. 2)

Solutions for Codeforces Round 917 (Div. 2) (contest 1917). 3/6 problems verified against sample I/O. Difficulty range: 800-2500.

6 items

Codeforces Round 917 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2500 | Time: 13m 23s

Problem Name Rating Tags Solve Time Verified
A Least Product 800 constructive-algorithms, math 3m 23s ✗
B Erase First or Second Letter 1100 brute-force, combinatorics, data-structures 1m 54s ✓
C Watering an Array 1600 brute-force, greedy, implementation 2m 13s ✓
D Yet Another Inversions Problem 2300 combinatorics, data-structures, dp 1m 48s ✗
E Construct Matrix 2500 constructive-algorithms, math 2m 9s ✗
F Construct Tree 2500 bitmasks, constructive-algorithms, dp 1m 56s ✓
Practice › Codeforces Solutions › Codeforces Round 917 (Div. 2) ›

CF 1917E - Construct Matrix

We are asked to construct an $n times n$ matrix of zeros and ones with two simultaneous constraints on the bitwise XORs of rows and columns, and an overall sum constraint.
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Practice › Codeforces Solutions › Codeforces Round 917 (Div. 2) ›

CF 1917A - Least Product

We are given an array of integers and the ability to decrease each number to any integer between zero and its current value. For positive numbers, this means we can reduce them to zero; for negative numbers, we can increase them toward zero.
codeforces competitive-programming constructive-algorithms math Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 917 (Div. 2) ›

CF 1917C - Watering an Array

We start with an array a of length n. For each of the next d days we must choose exactly one action. The first action increases the prefix [1..bi] by one, where the sequence b is generated by repeating the given array v forever. The second action scores points.
codeforces competitive-programming brute-force greedy implementation math Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 917 (Div. 2) ›

CF 1917D - Yet Another Inversions Problem

We are building a long array by interleaving two independent permutations in a structured way. One permutation, call it $p$, provides odd base values. The second permutation, $q$, determines powers of two.
codeforces competitive-programming combinatorics data-structures dp implementation math number-theory Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 917 (Div. 2) ›

CF 1917F - Construct Tree

We are given the lengths of all edges that must appear in a tree. The tree has exactly $n$ edges and $n+1$ vertices, so every length from the array is used exactly once as an edge weight.
codeforces competitive-programming bitmasks constructive-algorithms dp trees Jun 8, 2026
Practice › Codeforces Solutions › Codeforces Round 917 (Div. 2) ›

CF 1917B - Erase First or Second Letter

We are given a string and two operations: removing the first character or removing the second character of the current string. The task is to count how many distinct non-empty strings can be generated by applying these operations any number of times in any order.
codeforces competitive-programming brute-force combinatorics data-structures dp strings Jun 8, 2026