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LeetCode Topics

Array

Problem Name	Difficulty
0011-container-with-most-water	Medium
0026-remove-duplicates-from-sorted-array	Easy
0051-n-queens	Hard
0066-plus-one	Easy
0075-sort-colors	Medium
0085-maximal-rectangle	Hard
0088-merge-sorted-array	Easy
0121-best-time-to-buy-and-sell-stock	Easy
0122-best-time-to-buy-and-sell-stock-ii	Medium
0123-best-time-to-buy-and-sell-stock-iii	Hard
0189-rotate-array	Medium
0268-missing-number	Easy
0453-minimum-moves-to-equal-array-elements	Medium
0462-minimum-moves-to-equal-array-elements-ii	Medium
0705-design-hashset	Easy
0835-image-overlap	Medium
0905-sort-array-by-parity	Easy
0977-squares-of-a-sorted-array	Easy
1254-number-of-closed-islands	Medium
1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold	Medium
1464-maximum-product-of-two-elements-in-an-array	Easy
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum	Medium
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
1807-evaluate-the-bracket-pairs-of-a-string	Medium
1929-concatenation-of-array	Easy
2089-find-target-indices-after-sorting-array	Easy
2333-minimum-sum-of-squared-difference	Medium
2778-sum-of-squares-of-special-elements	Easy
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
2913-subarrays-distinct-element-sum-of-squares-i	Easy
2916-subarrays-distinct-element-sum-of-squares-ii	Hard
3414-maximum-score-of-non-overlapping-intervals	Hard
3483-unique-3-digit-even-numbers	Easy
3524-find-x-value-of-array-i	Medium
3525-find-x-value-of-array-ii	Hard
3551-minimum-swaps-to-sort-by-digit-sum	Medium
3619-count-islands-with-total-value-divisible-by-k	Medium
3644-maximum-k-to-sort-a-permutation	Medium
3665-twisted-mirror-path-count	Medium
3727-maximum-alternating-sum-of-squares	Medium
3736-minimum-moves-to-equal-array-elements-iii	Easy
3841-palindromic-path-queries-in-a-tree	Hard
3876-construct-uniform-parity-array-ii	Medium
3882-minimum-xor-path-in-a-grid	Medium
3886-sum-of-sortable-integers	Hard
3904-smallest-stable-index-ii	Medium
3942-minimum-operations-to-sort-a-permutation	Medium

Two Pointers

Problem Name	Difficulty
0011-container-with-most-water	Medium
0019-remove-nth-node-from-end-of-list	Medium
0026-remove-duplicates-from-sorted-array	Easy
0028-find-the-index-of-the-first-occurrence-in-a-string	Easy
0075-sort-colors	Medium
0088-merge-sorted-array	Easy
0189-rotate-array	Medium
0202-happy-number	Easy
0344-reverse-string	Easy
0680-valid-palindrome-ii	Easy
0876-middle-of-the-linked-list	Easy
0905-sort-array-by-parity	Easy
0977-squares-of-a-sorted-array	Easy
2472-maximum-number-of-non-overlapping-palindrome-substrings	Hard

Greedy

Problem Name	Difficulty
0011-container-with-most-water	Medium
0122-best-time-to-buy-and-sell-stock-ii	Medium
0678-valid-parenthesis-string	Medium
0680-valid-palindrome-ii	Easy
0921-minimum-add-to-make-parentheses-valid	Medium
1520-maximum-number-of-non-overlapping-substrings	Hard
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
2333-minimum-sum-of-squared-difference	Medium
2472-maximum-number-of-non-overlapping-palindrome-substrings	Hard
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
3723-maximize-sum-of-squares-of-digits	Medium
3727-maximum-alternating-sum-of-squares	Medium

String

Problem Name	Difficulty
0008-string-to-integer-atoi	Medium
0022-generate-parentheses	Medium
0028-find-the-index-of-the-first-occurrence-in-a-string	Easy
0043-multiply-strings	Medium
0168-excel-sheet-column-title	Easy
0171-excel-sheet-column-number	Easy
0301-remove-invalid-parentheses	Hard
0344-reverse-string	Easy
0459-repeated-substring-pattern	Easy
0520-detect-capital	Easy
0678-valid-parenthesis-string	Medium
0680-valid-palindrome-ii	Easy
0771-jewels-and-stones	Easy
0856-score-of-parentheses	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1096-brace-expansion-ii	Hard
1190-reverse-substrings-between-each-pair-of-parentheses	Medium
1520-maximum-number-of-non-overlapping-substrings	Hard
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
1807-evaluate-the-bracket-pairs-of-a-string	Medium
2390-removing-stars-from-a-string	Medium
2472-maximum-number-of-non-overlapping-palindrome-substrings	Hard
3498-reverse-degree-of-a-string	Easy
3841-palindromic-path-queries-in-a-tree	Hard
3863-minimum-operations-to-sort-a-string	Medium
3970-shortest-path-with-at-most-k-consecutive-identical-characters	Medium

String Matching

Problem Name	Difficulty
0028-find-the-index-of-the-first-occurrence-in-a-string	Easy
0459-repeated-substring-pattern	Easy

Z Algorithm

Problem Name	Difficulty
0028-find-the-index-of-the-first-occurrence-in-a-string	Easy
0459-repeated-substring-pattern	Easy

Knuth–Morris–Pratt Algorithm

Problem Name	Difficulty
0028-find-the-index-of-the-first-occurrence-in-a-string	Easy
0459-repeated-substring-pattern	Easy

Boyer–Moore String-Search Algorithm

Problem Name	Difficulty
0028-find-the-index-of-the-first-occurrence-in-a-string	Easy

Math

Problem Name	Difficulty
0043-multiply-strings	Medium
0066-plus-one	Easy
0070-climbing-stairs	Easy
0168-excel-sheet-column-title	Easy
0171-excel-sheet-column-number	Easy
0189-rotate-array	Medium
0202-happy-number	Easy
0231-power-of-two	Easy
0258-add-digits	Easy
0263-ugly-number	Easy
0268-missing-number	Easy
0326-power-of-three	Easy
0342-power-of-four	Easy
0367-valid-perfect-square	Easy
0453-minimum-moves-to-equal-array-elements	Medium
0462-minimum-moves-to-equal-array-elements-ii	Medium
0507-perfect-number	Easy
0836-rectangle-overlap	Easy
1281-subtract-the-product-and-sum-of-digits-of-an-integer	Easy
1401-circle-and-rectangle-overlapping	Medium
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
1621-number-of-sets-of-k-non-overlapping-line-segments	Medium
2235-add-two-integers	Easy
3524-find-x-value-of-array-i	Medium
3525-find-x-value-of-array-ii	Hard
3723-maximize-sum-of-squares-of-digits	Medium
3736-minimum-moves-to-equal-array-elements-iii	Easy
3871-count-commas-in-range-ii	Medium
3876-construct-uniform-parity-array-ii	Medium
3886-sum-of-sortable-integers	Hard

Simulation

Problem Name	Difficulty
0043-multiply-strings	Medium
0258-add-digits	Easy
1929-concatenation-of-array	Easy
2390-removing-stars-from-a-string	Medium
3498-reverse-degree-of-a-string	Easy

Hash Table

Problem Name	Difficulty
0202-happy-number	Easy
0268-missing-number	Easy
0705-design-hashset	Easy
0771-jewels-and-stones	Easy
1096-brace-expansion-ii	Hard
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum	Medium
1520-maximum-number-of-non-overlapping-substrings	Hard
1807-evaluate-the-bracket-pairs-of-a-string	Medium
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
2913-subarrays-distinct-element-sum-of-squares-i	Easy
2916-subarrays-distinct-element-sum-of-squares-ii	Hard
3483-unique-3-digit-even-numbers	Easy
3551-minimum-swaps-to-sort-by-digit-sum	Medium

Floyd's Cycle Finding Algorithm

Problem Name	Difficulty
0202-happy-number	Easy

Backtracking

Problem Name	Difficulty
0022-generate-parentheses	Medium
0051-n-queens	Hard
0301-remove-invalid-parentheses	Hard
1096-brace-expansion-ii	Hard

Algorithm X

Problem Name	Difficulty
0051-n-queens	Hard

Sorting

Problem Name	Difficulty
0075-sort-colors	Medium
0088-merge-sorted-array	Easy
0268-missing-number	Easy
0462-minimum-moves-to-equal-array-elements-ii	Medium
0905-sort-array-by-parity	Easy
0977-squares-of-a-sorted-array	Easy
1096-brace-expansion-ii	Hard
1464-maximum-product-of-two-elements-in-an-array	Easy
1520-maximum-number-of-non-overlapping-substrings	Hard
2089-find-target-indices-after-sorting-array	Easy
2333-minimum-sum-of-squared-difference	Medium
3414-maximum-score-of-non-overlapping-intervals	Hard
3551-minimum-swaps-to-sort-by-digit-sum	Medium
3727-maximum-alternating-sum-of-squares	Medium
3886-sum-of-sortable-integers	Hard

Dynamic Programming

Problem Name	Difficulty
0022-generate-parentheses	Medium
0070-climbing-stairs	Easy
0085-maximal-rectangle	Hard
0121-best-time-to-buy-and-sell-stock	Easy
0122-best-time-to-buy-and-sell-stock-ii	Medium
0123-best-time-to-buy-and-sell-stock-iii	Hard
0678-valid-parenthesis-string	Medium
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum	Medium
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
1621-number-of-sets-of-k-non-overlapping-line-segments	Medium
2472-maximum-number-of-non-overlapping-palindrome-substrings	Hard
3414-maximum-score-of-non-overlapping-intervals	Hard
3524-find-x-value-of-array-i	Medium
3665-twisted-mirror-path-count	Medium
3882-minimum-xor-path-in-a-grid	Medium

Stack

Problem Name	Difficulty
0085-maximal-rectangle	Hard
0678-valid-parenthesis-string	Medium
0856-score-of-parentheses	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1096-brace-expansion-ii	Hard
1190-reverse-substrings-between-each-pair-of-parentheses	Medium
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
2390-removing-stars-from-a-string	Medium

Matrix

Problem Name	Difficulty
0085-maximal-rectangle	Hard
0835-image-overlap	Medium
1254-number-of-closed-islands	Medium
3619-count-islands-with-total-value-divisible-by-k	Medium
3665-twisted-mirror-path-count	Medium
3882-minimum-xor-path-in-a-grid	Medium

Monotonic Stack

Problem Name	Difficulty
0085-maximal-rectangle	Hard

Binary Search

Problem Name	Difficulty
0268-missing-number	Easy
0367-valid-perfect-square	Easy
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum	Medium
2089-find-target-indices-after-sorting-array	Easy
2333-minimum-sum-of-squared-difference	Medium
3414-maximum-score-of-non-overlapping-intervals	Hard

Bit Manipulation

Problem Name	Difficulty
0231-power-of-two	Easy
0268-missing-number	Easy
0342-power-of-four	Easy
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
3644-maximum-k-to-sort-a-permutation	Medium
3841-palindromic-path-queries-in-a-tree	Hard
3882-minimum-xor-path-in-a-grid	Medium

Recursion

Problem Name	Difficulty
0203-remove-linked-list-elements	Easy
0231-power-of-two	Easy
0326-power-of-three	Easy
0342-power-of-four	Easy
3483-unique-3-digit-even-numbers	Easy

Linked List

Problem Name	Difficulty
0019-remove-nth-node-from-end-of-list	Medium
0083-remove-duplicates-from-sorted-list	Easy
0203-remove-linked-list-elements	Easy
0237-delete-node-in-a-linked-list	Medium
0328-odd-even-linked-list	Medium
0705-design-hashset	Easy
0876-middle-of-the-linked-list	Easy

Design

Problem Name	Difficulty
0705-design-hashset	Easy

Hash Function

Problem Name	Difficulty
0705-design-hashset	Easy

Heap (Priority Queue)

Problem Name	Difficulty
1464-maximum-product-of-two-elements-in-an-array	Easy
2333-minimum-sum-of-squared-difference	Medium
3970-shortest-path-with-at-most-k-consecutive-identical-characters	Medium

Prefix Sum

Problem Name	Difficulty
1621-number-of-sets-of-k-non-overlapping-line-segments	Medium
3904-smallest-stable-index-ii	Medium

Tree

Problem Name	Difficulty
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
2265-count-nodes-equal-to-average-of-subtree	Medium
3841-palindromic-path-queries-in-a-tree	Hard

Depth-First Search

Problem Name	Difficulty
1254-number-of-closed-islands	Medium
2265-count-nodes-equal-to-average-of-subtree	Medium
3619-count-islands-with-total-value-divisible-by-k	Medium
3841-palindromic-path-queries-in-a-tree	Hard

Binary Tree

Problem Name	Difficulty
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
2265-count-nodes-equal-to-average-of-subtree	Medium

Enumeration

Problem Name	Difficulty
2778-sum-of-squares-of-special-elements	Easy
3483-unique-3-digit-even-numbers	Easy
3886-sum-of-sortable-integers	Hard

Geometry

Problem Name	Difficulty
0836-rectangle-overlap	Easy
1401-circle-and-rectangle-overlapping	Medium

Combinatorics

Problem Name	Difficulty
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
1621-number-of-sets-of-k-non-overlapping-line-segments	Medium

Sliding Window

Problem Name	Difficulty
1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold	Medium
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum	Medium

Segment Tree

Problem Name	Difficulty
2913-subarrays-distinct-element-sum-of-squares-i	Easy
2916-subarrays-distinct-element-sum-of-squares-ii	Hard
3525-find-x-value-of-array-ii	Hard
3841-palindromic-path-queries-in-a-tree	Hard

Bracket Sequences

Problem Name	Difficulty
0022-generate-parentheses	Medium
0678-valid-parenthesis-string	Medium
0856-score-of-parentheses	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1190-reverse-substrings-between-each-pair-of-parentheses	Medium
1541-minimum-insertions-to-balance-a-parentheses-string	Medium

Breadth-First Search

Problem Name	Difficulty
0301-remove-invalid-parentheses	Hard
1096-brace-expansion-ii	Hard
1254-number-of-closed-islands	Medium
3619-count-islands-with-total-value-divisible-by-k	Medium

Database

Problem Name	Difficulty
0175-combine-two-tables	Easy
0181-employees-earning-more-than-their-managers	Easy
0196-delete-duplicate-emails	Easy
0596-classes-with-at-least-5-students	Easy

Shell

Problem Name	Difficulty
0193-valid-phone-numbers	Easy

Binary Indexed Tree

Problem Name	Difficulty
2913-subarrays-distinct-element-sum-of-squares-i	Easy
2916-subarrays-distinct-element-sum-of-squares-ii	Hard
3841-palindromic-path-queries-in-a-tree	Hard

Quicksort

Problem Name	Difficulty
0075-sort-colors	Medium

Bubble Sort

Problem Name	Difficulty
0075-sort-colors	Medium

Divide and Conquer

Problem Name	Difficulty
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
3841-palindromic-path-queries-in-a-tree	Hard

Union-Find

Problem Name	Difficulty
1254-number-of-closed-islands	Medium
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard
3619-count-islands-with-total-value-divisible-by-k	Medium

Binary Search Tree

Problem Name	Difficulty
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard

Memoization

Problem Name	Difficulty
0070-climbing-stairs	Easy
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard

Fermat's Little Theorem

Problem Name	Difficulty
1569-number-of-ways-to-reorder-array-to-get-same-bst	Hard

Number Theory

Problem Name	Difficulty
0258-add-digits	Easy

Graph Theory

Problem Name	Difficulty
3970-shortest-path-with-at-most-k-consecutive-identical-characters	Medium

Shortest Path

Problem Name	Difficulty
3970-shortest-path-with-at-most-k-consecutive-identical-characters	Medium