Codeforces Round 138 (Div. 1)

Solutions for Codeforces Round 138 (Div. 1) (contest 223). 3/4 problems verified against sample I/O. Difficulty range: 1700-3000.

4 items

Codeforces Round 138 (Div. 1)

Type: Div. 1 | Problems: 4 | Verified: 3/4 | Rating range: 1700-3000 | Time: 8m 30s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Bracket Sequence	1700	data-structures, expression-parsing, implementation	1m 41s	✓
B	Two Strings	1900	data-structures, dp, strings	1m 42s	✓
C	Partial Sums	1900	combinatorics, math, number-theory	1m 25s	✓
D	Spider	3000	geometry, graphs	3m 42s	✗

Practice › Codeforces Solutions › Codeforces Round 138 (Div. 1) ›

CF 223A - Bracket Sequence

We are given a string consisting only of four bracket characters: (, ), [ and ]. The string itself is not guaranteed to be balanced. Our task is to find a contiguous substring that forms a valid bracket sequence.

Practice › Codeforces Solutions › Codeforces Round 138 (Div. 1) ›

CF 223B - Two Strings

We are given two lowercase strings, s and t. The task is not simply to check whether t is a subsequence of s. We must answer a stronger question. Consider every possible way to obtain t as a subsequence of s.

Practice › Codeforces Solutions › Codeforces Round 138 (Div. 1) ›

CF 223C - Partial Sums

We start with an array of length n. One operation replaces every element with its prefix sum. After one operation: $$ai leftarrow sum{j=1}^{i} aj$$ After repeating this process k times, we must print the resulting array. The operation is linear and highly structured.

Practice › Codeforces Solutions › Codeforces Round 138 (Div. 1) ›

CF 223D - Spider

We are given a simple polygon whose vertices are listed in counterclockwise order. A spider starts at vertex s and wants to reach vertex t. The spider has two kinds of movement. The first move is walking along the polygon boundary.