https://leetcode.com/problems/continuous-subarray-sum/description/

Any subarray sum % k = 0 #medium #hashmap

https://leetcode.com/problems/subarray-sums-divisible-by-k/description/

Count subarrays divisible by k #medium #hashmap

https://leetcode.com/problems/all-oone-data-structure/description/

Count usage frequencies in O(1) #hard #hashmap #linked_list

https://leetcode.com/problems/longest-square-streak-in-an-array/description/


Longest quadratic subset #medium #hashmap #math

https://leetcode.com/problems/find-the-number-of-distinct-colors-among-the-balls/description/


Running colors counter #medium #hashmap

# 6.07.2025
[1865. Finding Pairs With a Certain Sum](https://leetcode.com/problems/finding-pairs-with-a-certain-sum/description/) medium


Design pairs counter; two lists, one changes #medium #hashmap

# 16.10.2025
[2598. Smallest Missing Non-negative Integer After Operations](https://leetcode.com/problems/smallest-missing-non-negative-integer-after-operations/description/) medium


First positive number can't be build by adding/subtracting value #medium #hashmap