# General Problem Solving

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This list is not exhaustive! If you wish to contribute more techniques, please email me at <woojiahao1234@gmail.com>
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1. Finding the median of data: focus on the definition of a median and model the solution after it
2. Sub-array problems: think about using sliding windows discussed under [arrays](https://interviews.woojiahao.com/data-structures/arrays "mention")
3. Sub-sequence problems: think about sorting (if possible)
4. $$O(n \log n)$$ upper bound (found using [runtime-predictions](https://interviews.woojiahao.com/other-technical-topics/runtime-predictions "mention"))
   1. Divide and conquer, similar to merge sort
   2. [arrays](https://interviews.woojiahao.com/data-structures/arrays "mention") manipulation + [binary-search](https://interviews.woojiahao.com/algorithms/binary-search "mention") such as prefix sums + binary search
   3. [sorting](https://interviews.woojiahao.com/algorithms/sorting "mention") + operations on sorted array
   4. [segment-trees](https://interviews.woojiahao.com/data-structures/graphs/trees/segment-trees "mention")+ iterating over all ranges
   5. Applying the sweep line algorithm if there are [intervals](https://interviews.woojiahao.com/algorithms/intervals "mention") + events
5. Minimum/maximum across queries: try using [heaps](https://interviews.woojiahao.com/data-structures/graphs/trees/heaps "mention") or [double-ended-queues](https://interviews.woojiahao.com/data-structures/queues/double-ended-queues "mention")
   1. [heaps](https://interviews.woojiahao.com/data-structures/graphs/trees/heaps "mention") can be used to track the minimum during any query
   2. [double-ended-queues](https://interviews.woojiahao.com/data-structures/queues/double-ended-queues "mention") can be used to represent the current maximum (as the front) and potential maximums (subsequent elements) in the event where the current maximum "expires"