Interview Questions

Counting sort

https://leetcode.com/problems/campus-bikes/

https://leetcode.com/problems/height-checker/

DSU
https://leetcode.com/problems/sentence-similarity-ii/ (DFS as well)

https://leetcode.com/problems/number-of-islands-ii/

https://leetcode.com/problems/most-stones-removed-with-same-row-or-column/

Searching in Sorted 2-D array
1. https://leetcode.com/problems/search-a-2d-matrix-ii/
2. https://leetcode.com/problems/search-a-2d-matrix/
3. https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix/

DAG/Topological sort
4. https://leetcode.com/problems/course-schedule/
5. https://leetcode.com/problems/course-schedule-ii
6. https://leetcode.com/problems/alien-dictionary/

https://leetcode.com/problems/longest-increasing-path-in-a-matrix/ (OR DFS with memo/DP)

https://leetcode.com/problems/all-paths-from-source-lead-to-destination/

https://leetcode.com/problems/network-delay-time/

(diagram gives the impression of DAG, but it's DG => Directed and cyclic, find the shortest path from source to all)

https://leetcode.com/problems/reorder-routes-to-make-all-paths-lead-to-the-city-zero/

Trie or other string match
7. https://leetcode.com/problems/add-and-search-word-data-structure-design/
8. https://leetcode.com/problems/wildcard-matching/ 

https://leetcode.com/problems/stream-of-characters/

https://leetcode.com/problems/design-search-autocomplete-system/
Similar:
https://leetcode.com/problems/word-ladder/
https://leetcode.com/problems/implement-magic-dictionary/

Heap
9. https://leetcode.com/problems/top-k-frequent-elements/
10. https://leetcode.com/problems/the-k-weakest-rows-in-a-matrix/

https://leetcode.com/problems/mean-of-array-after-removing-some-elements/

https://leetcode.com/problems/minimum-cost-to-hire-k-workers/

non heap approach as well

Graph
11. DFS => https://leetcode.com/problems/accounts-merge/
12. 2D Matrix BFS => https://leetcode.com/problems/walls-and-gates/
13. DFS => https://leetcode.com/problems/is-graph-bipartite
14. DFS => https://leetcode.com/problems/similar-string-groups/
15. BFS => https://leetcode.com/problems/word-ladder/
16. BFS => https://leetcode.com/problems/maximum-depth-of-n-ary-tree/
17. DFS => https://leetcode.com/problems/delete-nodes-and-return-forest/

https://leetcode.com/problems/android-unlock-patterns/  (And permutation generation)

BFS https://leetcode.com/problems/sliding-puzzle/

BFS https://leetcode.com/problems/evaluate-division/

Modified BFS https://leetcode.com/problems/shortest-path-in-a-grid-with-obstacles-elimination/
DFS => https://leetcode.com/problems/path-with-maximum-gold/ (backtracking)

DFS => https://leetcode.com/problems/minimum-time-to-collect-all-apples-in-a-tree/

https://leetcode.com/problems/find-root-of-n-ary-tree/

DFS => https://leetcode.com/problems/letter-tile-possibilities/

https://leetcode.com/problems/flower-planting-with-no-adjacent/

Matrix
18. https://leetcode.com/problems/range-sum-query-2d-immutable/

build upon this https://leetcode.com/problems/matrix-block-sum/
19. https://leetcode.com/problems/diagonal-traverse/
20. BFS => https://leetcode.com/problems/shortest-path-in-binary-matrix/
21. BFS => https://leetcode.com/problems/swim-in-rising-water
22. BFS => https://leetcode.com/problems/find-positive-integer-solution-for-a-given-equation/
23. BFS => https://leetcode.com/problems/shortest-distance-from-all-buildings/

https://leetcode.com/problems/find-valid-matrix-given-row-and-column-sums/

https://leetcode.com/problems/toeplitz-matrix/

Linked Lists
24. https://leetcode.com/problems/next-greater-node-in-linked-list/
25. https://leetcode.com/problems/merge-two-sorted-lists/
26. https://leetcode.com/problems/reorder-list/
27. https://leetcode.com/problems/insert-into-a-sorted-circular-linked-list/
28. https://leetcode.com/problems/convert-binary-search-tree-to-sorted-doubly-linked-list/

https://leetcode.com/problems/print-immutable-linked-list-in-reverse/

Stack
29. https://leetcode.com/problems/simplify-path/
30. Parentheses => https://leetcode.com/problems/valid-parentheses/

 https://leetcode.com/problems/brace-expansion/
https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/

https://leetcode.com/problems/remove-outermost-parentheses/

Interval merging/intersection/Task Scheduling
31. https://leetcode.com/problems/task-scheduler/

32. https://leetcode.com/problems/non-overlapping-intervals/ - sort by end time ascending, maximize number of tasks finished
33. https://leetcode.com/problems/minimum-number-of-arrows-to-burst-balloons - same as above, sort by end time

34. https://leetcode.com/problems/interval-list-intersections/
35. https://leetcode.com/problems/merge-intervals/ - start time ascending sort, keep merging with top of the stack
36. https://leetcode.com/problems/meeting-rooms/
https://leetcode.com/problems/maximum-number-of-events-that-can-be-attended/description/

sort by start day + minHeap OR sort by end day and iterate over day interval.

These 4 problems have exact same solution:
37. https://leetcode.com/problems/meeting-rooms-ii/
38. https://leetcode.com/problems/my-calendar-i/
39. https://leetcode.com/problems/my-calendar-ii/
40. https://leetcode.com/problems/my-calendar-iii/

41. https://leetcode.com/problems/data-stream-as-disjoint-intervals/

Binary Tree/Binary Search Tree
https://leetcode.com/problems/binary-tree-coloring-game/

https://leetcode.com/problems/all-possible-full-binary-trees/

https://leetcode.com/problems/peak-index-in-a-mountain-array/
https://leetcode.com/problems/find-in-mountain-array/

https://leetcode.com/problems/correct-a-binary-tree/

42. Inorder Traversal => https://leetcode.com/problems/binary-search-tree-iterator/
43. Inorder Traversal => https://leetcode.com/problems/validate-binary-search-tree/
44. InOrder => https://leetcode.com/problems/kth-smallest-element-in-a-bst
45. InOrder => https://leetcode.com/problems/increasing-order-search-tree

46. PostOrder => https://leetcode.com/problems/serialize-and-deserialize-binary-tree/
47. PostOrder => https://leetcode.com/problems/range-sum-of-bst/
48. PostOrder => https://leetcode.com/problems/flatten-binary-tree-to-linked-list
49. DFS (backtracking) https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/
50. DFS => https://leetcode.com/problems/lowest-common-ancestor-of-deepest-leaves
51. DFS https://leetcode.com/problems/all-nodes-distance-k-in-binary-tree/
52. BFS => https://leetcode.com/problems/check-completeness-of-a-binary-tree/
53. BFS => https://leetcode.com/problems/binary-tree-right-side-view/
54. https://leetcode.com/problems/binary-tree-vertical-order-traversal/
55. https://leetcode.com/problems/closest-binary-search-tree-value/
56. https://leetcode.com/problems/smallest-subtree-with-all-the-deepest-nodes/
57. https://leetcode.com/problems/minimum-depth-of-binary-tree/
58. https://leetcode.com/problems/binary-tree-longest-consecutive-sequence/
59. https://leetcode.com/problems/binary-tree-longest-consecutive-sequence-ii/
60. https://leetcode.com/problems/split-bst/
61. https://leetcode.com/problems/populating-next-right-pointers-in-each-node
62. https://leetcode.com/problems/univalued-binary-tree
63. https://leetcode.com/problems/diameter-of-binary-tree

Binary Search
64. https://leetcode.com/problems/missing-element-in-sorted-array/
65. https://leetcode.com/problems/random-pick-with-weight/
66. https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
67. https://leetcode.com/problems/first-bad-version/
68. https://leetcode.com/problems/fixed-point/
69. https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix

https://leetcode.com/problems/find-peak-element/


Continuous SubArray/SubString/SubSequence
70. https://leetcode.com/problems/subarray-sum-equals-k/
71. https://leetcode.com/problems/continuous-subarray-sum/
72. https://leetcode.com/problems/maximum-size-subarray-sum-equals-k/
73. https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/

similar to https://leetcode.com/problems/fruit-into-baskets/
74. https://leetcode.com/problems/find-all-anagrams-in-a-string/solution/
75. https://leetcode.com/problems/permutation-in-string/
76. https://leetcode.com/problems/max-consecutive-ones-iii/
77. https://leetcode.com/problems/longest-consecutive-sequence

https://leetcode.com/problems/sliding-window-maximum/

https://leetcode.com/problems/longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit/

https://leetcode.com/problems/shortest-way-to-form-string/

DP
78. https://leetcode.com/problems/partition-equal-subset-sum
79. https://leetcode.com/problems/minimum-cost-for-tickets/
80. https://leetcode.com/problems/longest-arithmetic-sequence/
81. https://leetcode.com/problems/decode-ways/
82. https://leetcode.com/problems/minimum-knight-moves/
83. https://leetcode.com/problems/target-sum/
84. https://leetcode.com/problems/maximal-square
85. https://leetcode.com/problems/word-break/
86. https://leetcode.com/problems/longest-line-of-consecutive-one-in-matrix
87. https://leetcode.com/problems/knight-probability-in-chessboard/
88. https://leetcode.com/problems/valid-palindrome-iii/
89. https://leetcode.com/problems/longest-palindromic-subsequence
90. https://leetcode.com/problems/number-of-ways-to-stay-in-the-same-place-after-some-steps/

91. https://leetcode.com/problems/how-many-apples-can-you-put-into-the-basket
92. https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iii/ (Check i, ii as well)
93. https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv

https://leetcode.com/problems/number-of-dice-rolls-with-target-sum/

https://leetcode.com/problems/perfect-squares/

https://leetcode.com/problems/campus-bikes-ii/

https://leetcode.com/problems/cherry-pickup-ii/

https://leetcode.com/problems/minimum-distance-to-type-a-word-using-two-fingers/

https://leetcode.com/problems/minimum-swaps-to-make-sequences-increasing/

https://leetcode.com/problems/odd-even-jump/

https://leetcode.com/problems/count-square-submatrices-with-all-ones/

contrast with https://leetcode.com/problems/count-submatrices-with-all-ones/

Array/List manipulation
94. https://leetcode.com/problems/move-zeroes/
95. https://leetcode.com/problems/nested-list-weight-sum-ii/ - also do (i)
96. https://leetcode.com/problems/squares-of-a-sorted-array/
97. https://leetcode.com/problems/product-of-array-except-self/

similar to https://leetcode.com/problems/minimum-number-of-operations-to-move-all-balls-to-each-box/
98. https://leetcode.com/problems/maximum-swap/
99. https://leetcode.com/problems/intersection-of-three-sorted-arrays/
100. https://leetcode.com/problems/remove-duplicates-from-sorted-array
101. https://leetcode.com/problems/single-row-keyboard/
102. https://leetcode.com/problems/decompress-run-length-encoded-list/
103. https://leetcode.com/problems/sort-array-by-parity-ii/
104. https://leetcode.com/problems/monotonic-array/

https://leetcode.com/problems/wiggle-sort/

Deep Copy
105. https://leetcode.com/problems/clone-graph/
106. https://leetcode.com/problems/copy-list-with-random-pointer/

Arithmetic operations/Math
107. https://leetcode.com/problems/multiply-strings/
108. https://leetcode.com/problems/divide-two-integers/ (Read the Solution section, quite good)
109. https://leetcode.com/problems/bulb-switcher/
110. https://leetcode.com/problems/fraction-to-recurring-decimal/
111. https://leetcode.com/problems/basic-calculator-ii/
112. Geometry => https://leetcode.com/problems/minimum-area-rectangle
113. https://leetcode.com/problems/largest-number/
114. https://leetcode.com/problems/projection-area-of-3d-shapes/
115. https://leetcode.com/problems/number-of-steps-to-reduce-a-number-to-zero
116. https://leetcode.com/problems/plus-one/

https://leetcode.com/problems/add-to-array-form-of-integer/

Generating permutations/combinations
117. https://leetcode.com/problems/next-permutation/
118. https://leetcode.com/problems/letter-combinations-of-a-phone-number/ (cross product of lists)
119. https://leetcode.com/problems/subsets (power set)

https://leetcode.com/problems/di-string-match/

String manipulation

120. https://leetcode.com/problems/camelcase-matching/
121. https://leetcode.com/problems/goat-latin/
122. https://leetcode.com/problems/custom-sort-string/
123. https://leetcode.com/problems/add-bold-tag-in-string/
124. Parentheses => https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/

125. https://leetcode.com/problems/longest-chunked-palindrome-decomposition/
126. Parentheses => https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/
127. https://leetcode.com/problems/remove-invalid-parentheses/
128. Parentheses => https://leetcode.com/problems/generate-parentheses/
129. https://leetcode.com/problems/reorganize-string/
130. https://leetcode.com/problems/find-and-replace-in-string/
131. https://leetcode.com/problems/implement-magic-dictionary/
132. https://leetcode.com/problems/group-shifted-strings/
133. https://leetcode.com/problems/subdomain-visit-count/
134. https://leetcode.com/problems/jewels-and-stones/
135. https://leetcode.com/problems/is-subsequence/
136. https://leetcode.com/problems/string-transforms-into-another-string/

similar to https://leetcode.com/problems/isomorphic-strings/

https://leetcode.com/problems/decode-string/

https://leetcode.com/problems/x-of-a-kind-in-a-deck-of-cards/

https://leetcode.com/problems/long-pressed-name/

https://leetcode.com/problems/repeated-substring-pattern/

Others
137. https://leetcode.com/problems/exam-room/

start from https://leetcode.com/problems/maximize-distance-to-closest-person/
138. https://leetcode.com/problems/next-closest-time
139. https://leetcode.com/problems/validate-ip-address/
140. https://leetcode.com/problems/unique-email-addresses/
141. https://leetcode.com/problems/flatten-nested-list-iterator/
142. https://leetcode.com/problems/logger-rate-limiter/
143. https://leetcode.com/problems/random-pick-index/
144. https://leetcode.com/problems/find-the-celebrity

145. https://leetcode.com/problems/3sum/

https://leetcode.com/problems/sentence-screen-fitting/

https://leetcode.com/problems/alphabet-board-path/

https://leetcode.com/problems/shortest-distance-to-target-color/

https://leetcode.com/problems/positions-of-large-groups/

https://leetcode.com/problems/robot-return-to-origin/

https://leetcode.com/problems/expressive-words/

https://leetcode.com/problems/rearrange-spaces-between-words/

https://leetcode.com/problems/confusing-number-ii/

https://leetcode.com/problems/bulls-and-cows/

https://leetcode.com/problems/design-phone-directory/

https://leetcode.com/problems/snapshot-array/

https://leetcode.com/problems/longest-absolute-file-path/

https://leetcode.com/problems/license-key-formatting/

https://leetcode.com/problems/k-empty-slots/