https://leetcode.com/problems/letter-tile-possibilities/description/


Count uniq sequences from letters #medium #backtracking

https://leetcode.com/problems/construct-smallest-number-from-di-string/description/



Smallest number from 1..9 and Inc-Dec pattern #medium #backtrack #greedy

https://leetcode.com/problems/the-k-th-lexicographical-string-of-all-happy-strings-of-length-n/description/


k`th string of `abc permutations #medium #backtracking

https://leetcode.com/problems/find-unique-binary-string/description/

Binary number not in a set #medium #backtracking

https://leetcode.com/problems/find-elements-in-a-contaminated-binary-tree/description/


Is number in a tree 2*v+(1L, 2R)? #medium #bfs #dfs

https://leetcode.com/problems/recover-a-tree-from-preorder-traversal/description/


Recover binary tree from depth-dashes string #hard #stack

https://leetcode.com/problems/construct-binary-tree-from-preorder-and-postorder-traversal/description/


Tree from preorder & postorder #medium #stack

https://leetcode.com/problems/most-profitable-path-in-a-tree/description/


Max Alice path down, Bob up in tree #medium #dfs

https://leetcode.com/problems/number-of-sub-arrays-with-odd-sum/description/


Count odd sum subarrays #medium #prefix_sum

https://leetcode.com/problems/maximum-absolute-sum-of-any-subarray/description/


Max abs of subarray sum #medium #prefix_sum

https://leetcode.com/problems/length-of-longest-fibonacci-subsequence/description/

Longest sequence a, b, a + b #medium #dynamic_programming

https://leetcode.com/problems/shortest-common-supersequence/description/


Shortest string with both subsequences #hard #lcs #dp

https://leetcode.com/problems/apply-operations-to-an-array/description/


If a[i] == a[i + 1], a[i] *= 2, a[i + 1] = 0 #easy

https://leetcode.com/problems/merge-two-2d-arrays-by-summing-values/description/


Merge two ascending [key, value] lists #easy

https://leetcode.com/problems/partition-array-according-to-given-pivot/description/


Partition around p #medium

Number as sum of distinct powers of 3 #medium #math


https://leetcode.com/problems/check-if-number-is-a-sum-of-powers-of-three/description/

Arithmetic sum #medium #math


https://leetcode.com/problems/count-total-number-of-colored-cells/description/

https://leetcode.com/problems/find-missing-and-repeated-values/description/


Missing and repeated in 1..n array #medium #math

Min diff primes pair in left..right #medium #math


https://leetcode.com/problems/closest-prime-numbers-in-range/

Min 'W' flips to make k 'B' #medium #sliding_window


https://leetcode.com/problems/minimum-recolors-to-get-k-consecutive-black-blocks/description