Problem 1: Valid String Check
Description:
Given a string, check if it is valid or not. A valid string must:
- Be divisible by 3 (interpreted as the numeric value of the string is divisible by 3).
- Contain the digit '7' at least twice.
Testcases:
Valid strings: 771, 777, 123777
Invalid strings: 12345, 71, 171, 70
Problem 2: Command Frequency Counter
Description:
You are given an array of commands. There are only three possible commands: cmd1, cmd2, and cmd3. Your task is to return an array of size 3 that contains the frequency of each command in the input array, in the order [frequency of cmd1, frequency of cmd2, frequency of cmd3].
Also, any element in the form of !<index> refers to the same command that was present at the position in the input array. Note that indexing starts from 1 (not 0).
Input:
[cmd1, cmd2, cmd3, !1, !2, cmd3, cmd1]Output:
[3, 2, 2]Explanation:
- At index 4 (
!1), the command is the same as the command at index 1 (cmd1). - At index 5 (
!2), the command is the same as the command at index 2 (cmd2).
Problem 3: Regional Maximum Finder
Difficulty: Medium or maybe Hard
Description:
You are given a 2D array. Your task is to find the regional maxima in the array and return a 2D array of size (X * 2) where each row contains the position [i, j] of a regional maximum.
Definition of Regional Maximum:
A cell (i, j) is considered a regional maximum if:
array[i][j] != 0array[i][j]is the maximum value within its region.
Definition of Region:
For a cell (i, j) with value cell:
- The region is defined as the rectangular area
(i - cell to i + cell) * (j - cell to j + cell). - Exclude the corner cells from above:
(i - cell, j - cell), (i - cell, j + cell), (i + cell, j - cell), and (i + cell, j + cell). - If the calculated region goes out of bounds, ignore those out-of-bound cells.
Input:
[
[3, 0, 1],
[2, 0, 0],
[0, 0, 0],
]Output:
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