https://leetcode.com/problems/lexicographical-numbers/description/

Lexicographical ordered numbers 1..n #medium #dfs

https://leetcode.com/problems/k-th-smallest-in-lexicographical-order/description/

k lexicographically smallest value from 1..n #hard #math

https://leetcode.com/problems/extra-characters-in-a-string/description/

Min extra chars to form an s from dictionary #medium #dynamic_programming

https://leetcode.com/problems/find-the-length-of-the-longest-common-prefix/description/


Common digit prefix between all pairs of two num arrays #medium #trie

https://leetcode.com/problems/sum-of-prefix-scores-of-strings/description/

Counts of words with same prefixes #hard #trie

https://leetcode.com/problems/my-calendar-i/description/

Insert non-intersection interval #medium #binary_search

https://leetcode.com/problems/my-calendar-ii/description/

Add intervals intersecting less than two times #medium #line_sweep

https://leetcode.com/problems/design-circular-deque/description/

Ring buffer #medium

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