Two coding problems were asked in a phone screen for a Software Engineer role: 1. **Count contiguous segments with a target sum** Given an integer array `nums` and an integer `k`, return the number of contiguous subarrays whose sum is exactly `k`. **Follow-up:** How would you handle this if the input were extremely large or arrived as a stream, so you could not store the full array in memory? Describe what information you would maintain online and the time/space trade-offs. 2. **Count independent building communities in a city grid** You are given a 2D grid representing a city map, where `1` means a building and `0` means empty land. Two building cells belong to the same community if they are adjacent vertically or horizontally. Return the number of distinct communities. **Follow-up:** If the grid is very large, how would you adapt your approach to avoid issues with recursion depth, memory usage, or loading the entire grid at once?