Friday the 13th, Programmers Day

7 problems from Friday the 13th, Programmers Day (contest 345), difficulty 1500-2700. 6/7 solutions verified against sample I/O.

7 items

Friday the 13th, Programmers Day

Special | 7 problems | 6/7 verified | Difficulty 1500-2700 | 13m 16s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Expecting Trouble	1500	*special, probabilities	532	1m 36s	✓
B	Triskaidekaphobia	2100	*special	129	1m 47s	✓
C	Counting Fridays	2000	*special	130	1m 43s	✓
D	Chain Letter	2200	*special, dfs-and-similar, graphs	83	1m 27s	✓
E	Black Cat Rush	2700	*special	55	1m 16s	✓
F	Superstitions Inspection	2700	*special	52	1m 54s
G	Suffix Subgroup	2200	*special, strings	105	3m 33s	✓

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CF 345F - Superstitions Inspection

The input is not given in the usual structured format with counts. Instead, it is a small text file that alternates between country names and lists of superstitions. A line that does not start with is a country name.

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CF 345C - Counting Fridays

We are given a small list of contest dates. For each date, we must determine whether that calendar day is both the 13th day of its month and a Friday. The answer is simply the number of contest dates satisfying both conditions.

Practice › Codeforces Solutions › Friday the 13th, Programmers Day ›

CF 345G - Suffix Subgroup

We are given a list of strings, and the task is to find the largest possible subset of these strings such that all strings in the subset are suffixes of some single string. In other words, there should exist a string t that ends with every string in our chosen subset.

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CF 345B - Triskaidekaphobia

We are given a number $n le 10^5$. For every integer base $b ge 2$, we write $n$ in base $b$, but instead of usual digit symbols we represent each digit as a decimal number and concatenate them without separators.

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CF 345E - Black Cat Rush

We are moving along a straight line from (0, 0) to (a, 0) at a constant speed v. Around us, there are n black cats, each starting at a point (xi, yi). Each cat can move in any direction at speed at most u.

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CF 345D - Chain Letter

We are given a network of people, where every pair of people either knows each other in both directions or does not know each other at all.

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CF 345A - Expecting Trouble

We are given a string representing Fridays the 13th across some period of time. Each character in the string can be "0" for a normal day, "1" for a particularly bad day, or "?" for a day the user cannot recall.