https://leetcode.com/problems/design-a-number-container-system/description/


Smallest running index of number in map #medium #treeset

https://leetcode.com/problems/count-number-of-bad-pairs/description/


Count pairs a[i] - a[j] != j - i #medium #counting #sorting

https://leetcode.com/problems/clear-digits/description/


Remove [char][digit] pairs from string #easy

https://leetcode.com/problems/remove-all-occurrences-of-a-substring/description/


Remove substring recursively #medium

https://leetcode.com/problems/max-sum-of-a-pair-with-equal-sum-of-digits/description/


Max pairs sum with equal digits sum #medium

https://leetcode.com/problems/minimum-operations-to-exceed-threshold-value-ii/description/


Count nums += min(x,y)*2+max(x,y) < k #medium #heap

https://leetcode.com/problems/product-of-the-last-k-numbers/description/

Running suffix product #medium #math #prefix_product

https://leetcode.com/problems/find-the-punishment-number-of-an-integer/description/


Sum x^2 if it's string partition sum = x #medium #backtracking

https://leetcode.com/problems/construct-the-lexicographically-largest-valid-sequence/description/


Construct array x = 1..n, a[i] = x, a[i + x] = x #medium #backtracking

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