Yandex.Algorithm Open 2011: Qualification 1

Solutions for Yandex.Algorithm Open 2011: Qualification 1 (contest 81). 3/5 problems verified against sample I/O. Difficulty range: 1400-2700.

5 items

Yandex.Algorithm Open 2011: Qualification 1

Type: Special | Problems: 5 | Verified: 3/5 | Rating range: 1400-2700 | Time: 13m 8s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Plug-in	1400	implementation	1m 36s	✓
B	Sequence Formatting	1700	implementation, strings	1m 43s	✓
C	Average Score	1700	greedy, math, sortings	3m 31s	✓
D	Polycarp's Picture Gallery	2100	constructive-algorithms, greedy	2m 48s	✗
E	Pairs	2700	dfs-and-similar, dp, dsu	3m 30s	✗

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81A - Plug-in

We are given a lowercase string that may contain accidental repeated keystrokes. Whenever two equal characters become adjacent, both characters must be deleted. After removing one pair, new adjacent equal pairs may appear, and those must also be removed.

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81B - Sequence Formatting

We are given a messy textual representation of a sequence. The string may contain positive integers, commas, spaces, and the special token .... Spaces may appear in the wrong places or appear multiple times. The task is purely formatting.

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81C - Average Score

We are given a sequence of marks, but the subject for each mark was lost. There are only two subjects, and we know exactly how many marks belong to each one. If subject 1 must receive a marks, then subject 2 automatically receives b = n - a marks.

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81D - Polycarp's Picture Gallery

We have several photo albums. Album i contains a[i] photos. We must build a cyclic gallery containing exactly n photos. Instead of choosing concrete photo IDs, we only need to output the album number for each position. The gallery is circular, so every position has two neighbors.

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81E - Pairs

Each student points to exactly one other student, the person they consider their best friend. We may create a pair (a, b) only if either a chose b or b chose a. Every student can belong to at most one pair.