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

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

https://leetcode.com/problems/design-a-stack-with-increment-operation/description/

Stack with range increment operation #medium #design

https://leetcode.com/problems/check-if-array-pairs-are-divisible-by-k/description/

Can all pairs sums be k-even? #medium #modulo

https://leetcode.com/problems/rank-transform-of-an-array/description/

Array values to their sorted set positions #easy

https://leetcode.com/problems/make-sum-divisible-by-p/description/

Min removed subarray length to make remainder % p = 0 #medium #modulo

https://leetcode.com/problems/divide-players-into-teams-of-equal-skill/description/


Sum of products of pairs with equal sums #medium #math

https://leetcode.com/problems/permutation-in-string/description/


Is s2 contains permutation of s1? #medium #two_pointers

https://leetcode.com/problems/sentence-similarity-iii/description/


Are strings equal after inserting substring? #medium

https://leetcode.com/problems/minimum-string-length-after-removing-substrings/description/


Remove 'AB' and 'CD' from the string #easy #stack

https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/description/


Min swaps to balance brackets #medium #two_pointers #stack

https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/description/


Minimum inserts to balance brackets #medium #stack

https://leetcode.com/problems/maximum-width-ramp/description/


Max j-i between a[i] <= a[j] in array #medium #monotonic_stack #sorting

https://leetcode.com/problems/the-number-of-the-smallest-unoccupied-chair/description/


target's chair number when chairs reused by multiple [arrival, leave] times #medium #sorting #heap

https://leetcode.com/problems/divide-intervals-into-minimum-number-of-groups/description/


Count non-intersecting groups of intervals #medium #heap #sorting

https://leetcode.com/problems/smallest-range-covering-elements-from-k-lists/description/


Smallest intersection of k sorted lists #medium #heap #tree_set

https://leetcode.com/problems/maximal-score-after-applying-k-operations/description/


Replace max(arr) with ceil(max/3) k times #medium #heap

https://leetcode.com/problems/separate-black-and-white-balls/description/

Min moves to sort 01 string #medium #greedy

https://leetcode.com/problems/longest-happy-string/description/


Longest string of a, b, c not repeating 3 times #medium #greedy

https://leetcode.com/problems/maximum-swap/description/

Max number after a single digits swap #medium #greedy

https://leetcode.com/problems/count-number-of-maximum-bitwise-or-subsets/description/


Count subsequences with max bitwise or #medium #backtracking