Operation Early Finish

HR has dumped the staff list into data/staff.csv (90 staff). The first line is a heading. Each line is staff_id,department,years_service,salary.

Your task: Store each member of staff as a record in a 1-D array of records. Only staff with 5 or more years’ service count. Which department has the highest total salary for those staff, and what is that total?

Answer format: department-total in lower case, e.g. maths-50000
Skills: records, reading a CSV file into an array of records, selection, totals per category, find the maximum

Evidence file: staff.csv (also in the evidence bag)

HINT: Use a dataclass for the record and convert years_service and salary to integers when you read each line. Skip the heading line. Keep a total for each department, then find the biggest.

The IT office has dumped 132 passwords into data/passwords.txt (one per line, a few contain spaces). A password is valid only if it follows every rule:

• at least 10 characters
• at least one capital letter and at least one lower case letter
• at least one digit
• at least one of these symbols: ! # $ % & * (a dash, full stop or underscore does not count)
• no spaces
• must not contain the word password, in any mix of capitals and lower case

Your task: Count how many passwords are valid. Write one function that checks a single password and returns True or False, then call it for each line.

Answer format: A whole number
Skills: validation, sub-program with a parameter returning a Boolean, string handling, counting

Evidence file: passwords.txt (also in the evidence bag)

HINT: Check one rule at a time. Use .isupper(), .islower(), .isdigit() on each character, and the “in” operator for the symbols. For “password”, convert to lower case first. Remember the newline at the end of each line.

Somebody has been guessing passwords on the school server. The log is data/access.log: a heading line, then lines like 07:15:02,10.0.4.23,FAIL (time, IP address, result). The result is OK or FAIL, but the logging software is sloppy: a failure can be written FAIL, Fail or fail.

Your task: Find the IP address with the most failed logins and say how many it had.

Answer format: ip-count, e.g. 10.0.1.5-2
Skills: reading a file, splitting lines, counting occurrences per category, case-insensitive comparison, find the maximum

Evidence file: access.log (also in the evidence bag)

HINT: Split each line on the comma. Compare the result using .upper() or .lower() so Fail and fail both count. Keep a count for each IP address (a dictionary is the neat way, or two parallel arrays).

150 lockers and their 4-digit combinations are in data/lockers.csv (lines look like L001,0517). Careful: some combinations start with a 0. A combination is rising if every digit is bigger than the digit before it, so 0358 and 1469 are rising but 1233 and 5731 are not.

Your task: Count the lockers with a rising combination, and give the locker number of the last one in the file. Write a function that takes a combination and returns True or False.

Answer format: count-locker in lower case, e.g. 2-l003
Skills: reading a file, splitting strings, text vs number, comparing neighbouring characters, sub-program returning a Boolean

Evidence file: lockers.csv (also in the evidence bag)

HINT: Keep the combination as TEXT. If you turn it into an integer the leading 0 vanishes. Compare each character with the next one. Update a “last found” variable every time you find a rising one.

The tuck shop has written its week into data/tuckshop.csv: a heading line, then item,category,price_pence,sold (an item that did not sell has 0 sold). Revenue for an item is price × number sold.

Your task: Which category made the most money in total, and how many pence was that? Write a function that takes the array of records and a category name and returns that category’s total revenue, then call it for each category.

Answer format: category-pence in lower case, e.g. snacks-1275
Skills: records, parameter passing (array and string), totals per category, find the maximum

Evidence file: tuckshop.csv (also in the evidence bag)

HINT: Skip the heading line. Make a list of the five category names, then loop through it and call your function for each one. Keep track of the biggest total AND which category it belonged to.

An encrypted message is in data/secret.txt. Every letter was shifted forward through the alphabet by an amount taken from a repeating keyword: VAULT. The first letter of the message moves by V (21 places, since A = 0), the second by A (0), the third by U (20), then L (11), T (19), and then the keyword starts again. Spaces and full stops are left alone and do not use up a keyword letter.

Your task: Decrypt the message. The passphrase is hidden inside it.

Answer format: The passphrase in lower case
Skills: ASCII codes (ord and chr), modular arithmetic, keeping a separate position in the keyword, string building

Evidence file: secret.txt (also in the evidence bag)

HINT: Keep a separate counter for the keyword position that only goes up when you meet a letter. Shift = ord(keyword letter) - 65. To go backwards: (ord(letter) - 65 - shift) % 26 + 65.

A sensor on the vault wall records temperature changes as 8-bit two’s complement binary numbers. The tape is in data/sensor.txt (64 readings, one per line, such as 11111100). The leftmost bit is the sign bit.

Your task: Convert every reading to the signed denary number it stores. Give the total of all the readings and how many are negative. (Do not just use int(reading, 2) on its own: that treats the sign bit as an ordinary bit.)

Answer format: total-negatives, e.g. 5-2 (the total can be negative: write it as -12-30)
Skills: two’s complement, binary to denary conversion, reading a file, running total, counting

Evidence file: sensor.txt (also in the evidence bag)

HINT: If the first bit is 1 the number is negative: the leftmost bit is worth −128 instead of +128. So value = int(reading, 2), then subtract 256 if the first character is ‘1’.

The vault’s inner door only opens for twin primes: two prime numbers that differ by exactly 2, like 11 and 13.

Your task: Count the pairs of twin primes where both numbers are below 10000, and give the smaller number of the largest pair.

Answer format: count-smaller, e.g. 4-17
Skills: sub-program to test for a prime, nested loops, efficient algorithm design

HINT: Write is_prime(number) first and test it. You only need to try divisors up to the square root of the number, and you can stop at the first divisor you find. Then check number and number + 2.

data/board.txt is a 20 × 20 minesweeper board: * is a mine, . is a safe square.

Your task: Every safe square shows how many of its (up to 8) neighbours are mines. Give the total of all the numbers on safe squares and the largest single number on the board.

*..
...
..*

Answer format: total-largest, e.g. 6-2
Skills: 2-D arrays, nested loops, boundary checking, standard algorithms

Evidence file: board.txt (also in the evidence bag)

HINT: For each safe square, check all 8 neighbours with two small loops (row offset and column offset, each from -1 to +1, skipping 0,0). Check you do not fall off the edge of the board.

The vault is full of old pipework. data/vault.txt is a 14 × 14 map: . is open pipe and # is a blockage. Water starts in the top-left corner and must reach the bottom-right corner, moving only right or down one square at a time, never through a #.

Your task: How many different routes can the water take?

..#
...
#..

Answer format: A whole number (it will be big, so do not try to list every route)
Skills: 2-D arrays, nested loops, algorithm design (build up the answer square by square)

Evidence file: vault.txt (also in the evidence bag)

HINT: Do not try to trace every route. Make a second grid of the same size where each square holds the number of routes that reach it. A square’s count is the count above it plus the count to its left (or 0 if it is a #).