Solve three coding interview problems

You are given three independent coding questions.

1) Decode an encoded string

Given an encoded string s, decode it using the following rule:

• Patterns of the form k[encoded_string] mean that encoded_string is repeated exactly k times.
• k is a positive integer and may have multiple digits.
• Encoded strings may be nested.

Example: s = "3[a2[c]]" should decode to "accaccacc".

Task: Return the decoded string.

Assumptions/constraints (you may state any reasonable ones in your solution):

• s contains only digits, letters, and brackets [ ] .
• The input is valid (balanced brackets, well-formed encoding).

2) Max profit with jump decisions

Given a 1D array arr of integers and starting at index 0, you can make a decision at each index i:

• Take : gain profit arr[i] , then jump to index i + 1 + arr[i] .
• Skip : gain profit 0 , then move to index i + 1 .

You may stop when your index is out of bounds (i.e., i >= n).

Task: Compute the maximum total profit achievable.

Follow-up

How does your approach change if arr can contain negative numbers?

• If you take at index i , you still gain arr[i] , and you still move to index i + 1 + arr[i] (which could move backward if arr[i] < 0 ).
• Clarify any assumptions needed to ensure termination and handle potential cycles.

3) Count connected land components in a grid

Given an m x n grid of characters '1' and '0':

• '1' represents land
• '0' represents water

Two land cells are connected if they are adjacent horizontally or vertically (4-directional adjacency).

Task: Return the number of connected components of land (i.e., the number of “islands”).

Example:

1 1 0
0 1 0
1 0 1

Answer: 3.