https://shio-chan-dev.github.io/jeanblog/tags/prefix-sum/Recent content in Prefix Sum on Jeanphilo BlogHugo -- 0.159.2en-usMon, 09 Feb 2026 13:19:45 +0800https://shio-chan-dev.github.io/jeanblog/alg/leetcode/hot100/560-subarray-sum-equals-k/Mon, 09 Feb 2026 13:19:45 +0800https://shio-chan-dev.github.io/jeanblog/alg/leetcode/hot100/560-subarray-sum-equals-k/Count subarrays whose sum equals k in O(n) using prefix sum and frequency hash map, with engineering scenarios, pitfalls, and runnable multi-language implementations.https://shio-chan-dev.github.io/jeanblog/alg/leetcode/437-path-sum-iii/Wed, 04 Feb 2026 16:02:26 +0800https://shio-chan-dev.github.io/jeanblog/alg/leetcode/437-path-sum-iii/Count downward paths in a binary tree whose sum equals targetSum in O(n) using prefix sums and a frequency hash map, with derivation, engineering mapping, and multi-language implementations.