Total Duration: 120 min

Number of Questions: 5

Each question has a time limit, unused time can be accumulated for later questions. You cannot go back to previous questions.

Question One:

5-minute time limit

Starting letter is “A”

input: “BZA” uppercase English letters

output: 4

explanation: A → B = 1, B → Z = 2, Z->A = 1. TOTAL: 1+2+1=4

There seems to be a similar original question, but I forgot. The difficulty is not high, mainly due to the tight time constraint.

Question Two:

20-minute time limit

string contains only | and *

input: string = "|**|*|", startIndex = [1, 1], endIndex[5, 6]
output: [2, 3]
explanation: Index starts from 1. In the range [1, 5], the number of asterisks (*) included

Approach:

Record the indexes of all ‘|’ and the number of stars before this index, using binary search and presum.

Result:

Normal test cases cause TLE, it feels like DP optimization is needed. The difficulty seems somewhat hard.

Question Three:

25 minutes

Subarray inversion

Find all subarrays of length three. Can only remove digits, cannot change the order.

input: [5, 4, 2, 1]

output: [5, 4, 2], [5, 4, 1], [5, 2, 1], [4, 2, 1], return the integer 4

Approach:

Backtrack with memorization.

Result:

Couldn’t optimize with DP, about half of the test cases cause TLE.

Question Four:

30 minutes

Convert Roman numerals to decimal, return sorted integers

1: I, 10: X, 50: L.

input: [“XI”, “XL”, “LX”]

output: [6, 40, 60]

Couldn’t complete it.

Question Five:

1 hour

Difficulty too high, not attempted, related to linked lists and DP.

Overall Impression:

The difficulty of the completely exceeds my level, writing up to a certain point makes me feel overwhelmed. Hope if anyone finds the original questions, they can share the question numbers for everyone’s benefit!