# ACM North Central North America Regional Programming Contest

Problem Clarifications

Ordered by problem number and time of posting

Problem 1 - Secret Decoder Ring

Clarification 1 (12:30 PM)
Although a byte is usually considered as having 8 bits, only the low-order 7 bits are used in this problem. In the Example section of the problem statement, 8 bits are shown for the characters 'A' and 'T', but only the 7 low-order bits are actually used. The bit identified as "bit 0" is the low-order bit.

Problem 2 - Do The Binary Shuffle

No clarifications.

Problem 3 - The Octavia Traffic Lights

No clarifications.

Problem 4 - Bridge Construction

Clarification 1 (12:30 PM)
In the third paragraph, the first sentence should read as follows (the change is indicated in red): "Of course, when the traffic flow is from east to west, any cars arriving on the west end must wait; similarly, if the traffic is moving across the bridge from west to east, cars arriving at the east end must wait."
Clarification 2 (4:04 PM)
When a car arrives at the bridge, if it can begin crossing, then it MUST begin crossing.

Problem 5 - Clock Repair

Clarification 1 (12:30 PM)
A cuckoo clock cuckoos only once per hour, precisely on the hour. That is, a clock will cuckoo when it displays 12:00, 1:00, 2:00, and so forth. Of course, the displayed time (when it cuckoos) may not be the actual time, since the clock may be running too fast or too slow.

Problem 6 - Arbitrary Multiplication

Clarification 1 (12:30 PM)
Both integers, X and Y, will be non-negative.

Problem 7 - Genome Matching

Clarification 1 (12:30 PM)
A line is missing in the Sample Input. The next to the last line (TCCAAGTCCCGGATCGA.) should appear twice.
Clarification 2 (12:30 PM)
Gene matches may overlap in a DNA sequence. For example, if a gene is ACA and the sample is ACACACA, your program should report three matches, one at index 1, one at index 3, and one at index 5.
Clarification 3 (12:30 PM)
There is a typographical error in the next to the last line of text on the first page of the problem statement. The text "Blond_Hair" should be "Blond_hair".
Clarification 4 (12:30 PM)
Whitespace consists of blanks and/or tab characters.

Problem 8 - Look, Ma! No Ruler!

No clarifications.

Problem 9 - Hex Carries

Clarification 1 (1:51 PM)
Each of the numbers is to be treated as a positive number. That is, there are no negative numbers ("-" is not a legal input character).

Clarifications will be used to amend the text of the published problem statements after the contest. These will appear on the regional website.