150 DSA questions for your next interview

Practice these questions to get the confidence and skills for your next coding interview.

Connect with me: https://linktr.ee/brwnboi

Arrays

Easy

• https://leetcode.com/problems/roman-to-integer/
• https://leetcode.com/problems/valid-parentheses/
• https://leetcode.com/problems/remove-duplicates-from-sorted-array/
• https://leetcode.com/problems/remove-element/
• https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
• https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/
• https://leetcode.com/problems/intersection-of-two-arrays-ii/
• https://leetcode.com/problems/single-number/
• https://leetcode.com/problems/contains-duplicate/
• https://leetcode.com/problems/plus-one/
• https://leetcode.com/problems/move-zeroes/
• https://leetcode.com/problems/rotate-image/

Medium

• https://leetcode.com/problems/3sum/
• https://leetcode.com/problems/4sum/
• https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
• https://leetcode.com/problems/group-anagrams/
• https://leetcode.com/problems/reduce-array-size-to-the-half/
• https://leetcode.com/problems/merge-intervals/

Linked list

Easy

• https://leetcode.com/problems/delete-node-in-a-linked-list/
• https://leetcode.com/problems/remove-nth-node-from-end-of-list/
• https://leetcode.com/problems/merge-two-sorted-lists/
• https://leetcode.com/problems/palindrome-linked-list/
• https://leetcode.com/problems/linked-list-cycle/

Medium

• https://leetcode.com/problems/intersection-of-two-linked-lists/
• https://leetcode.com/problems/remove-linked-list-elements/
• https://leetcode.com/problems/middle-of-the-linked-list/
• https://leetcode.com/problems/merge-k-sorted-lists/

Binary search

Easy

• https://leetcode.com/problems/binary-search/
• https://leetcode.com/problems/intersection-of-two-arrays/
• https://leetcode.com/problems/first-bad-version/
• https://leetcode.com/problems/arranging-coins/
• https://leetcode.com/problems/search-insert-position/

Medium

• https://leetcode.com/problems/search-in-rotated-sorted-array/
• https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
• https://leetcode.com/problems/kth-smallest-element-in-a-bst/
• https://leetcode.com/problems/find-peak-element/
• https://leetcode.com/problems/split-array-largest-sum/

Sliding window

Read

• Leetcode Pattern 2 | Sliding Windows for Strings | by csgator | Leetcode Patterns

Easy/Medium

• https://leetcode.com/problems/longest-substring-without-repeating-characters/
• https://leetcode.com/problems/find-all-anagrams-in-a-string/description/
• https://leetcode.com/problems/minimum-window-substring/description/
• https://leetcode.com/problems/count-number-of-nice-subarrays/
• https://leetcode.com/problems/fruit-into-baskets/

2 pointers

• https://leetcode.com/problems/intersection-of-two-arrays/
• https://leetcode.com/problems/maximum-ascending-subarray-sum/
• https://leetcode.com/problems/backspace-string-compare/
• https://leetcode.com/problems/long-pressed-name/
• https://leetcode.com/problems/fruit-into-baskets/
• https://leetcode.com/problems/max-consecutive-ones-iii/
• https://leetcode.com/problems/container-with-most-water/

Stacks, Queues

• Easy
• https://leetcode.com/problems/valid-parentheses/
• https://leetcode.com/problems/implement-queue-using-stacks/
• https://leetcode.com/problems/min-stack/
• Medium
• https://leetcode.com/problems/design-circular-queue/
• https://leetcode.com/problems/decode-string/
• https://leetcode.com/problems/open-the-lock/
• https://leetcode.com/problems/daily-temperatures/
• https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/

BFS, DFS

Read

• Leetcode Pattern 1 | BFS + DFS == 25% of the problems — part 1
• Leetcode Pattern 1 | DFS + BFS == 25% of the problems — part 2

Questions

• https://leetcode.com/problems/flood-fill/
• https://leetcode.com/problems/binary-tree-preorder-traversal/
• https://leetcode.com/problems/number-of-islands/
• https://leetcode.com/problems/walls-and-gates/
• https://leetcode.com/problems/max-area-of-island/
• https://leetcode.com/problems/number-of-provinces/
• https://leetcode.com/problems/perfect-squares/
• https://leetcode.com/problems/course-schedule/
• https://www.geeksforgeeks.org/detect-cycle-undirected-graph/
• https://leetcode.com/problems/word-ladder/
• https://leetcode.com/problems/01-matrix/
• https://leetcode.com/problems/rotting-oranges/
• https://leetcode.com/problems/perfect-squares/
• https://leetcode.com/problems/all-paths-from-source-to-target/
• https://leetcode.com/problems/number-of-closed-islands/

Recursion

Easy

• 509. Fibonacci Number
• Reverse String
• 24. Swap Nodes in Pairs
• 206. Reverse Linked List
• Leetcode #700 Search in a Binary Search Tree
• 70. Climbing Stairs
• Leetcode #50 Pow(x, n)

Backtracking

Read

• Leetcode Pattern 3 | Backtracking | by csgator | Leetcode Patterns
• A general approach to backtracking questions in Java (Subsets, Permutations, Combination Sum, Palindrome Partitioning)

Easy

• Word Search
• Leetcode #78 Subsets
• 90. Subsets II
• Letter Case Permutation

Medium

• 39. Combination Sum
• 17. Letter Combinations of a Phone Number
• Combinations
• Leetcode : Combination Sum II
• 216. Combination Sum III
• Combination Sum IV
• 46. Permutations
• 47. Permutations II
• 31. Next Permutation
• 51. N-Queens

Trees

Read

• Leetcode Pattern 0 | Iterative traversals on Trees | by csgator | Leetcode Patterns

Easy

• https://leetcode.com/problems/binary-tree-preorder-traversal/
• https://leetcode.com/problems/binary-tree-inorder-traversal/
• https://leetcode.com/problems/binary-tree-postorder-traversal/
• https://leetcode.com/problems/validate-binary-search-tree/
• https://leetcode.com/problems/minimum-distance-between-bst-nodes/
• https://leetcode.com/problems/symmetric-tree/
• https://leetcode.com/problems/same-tree/
• https://leetcode.com/problems/path-sum/
• https://leetcode.com/problems/maximum-depth-of-binary-tree/
• https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
• Medium
• https://leetcode.com/problems/validate-binary-search-tree/
• https://leetcode.com/problems/binary-search-tree-iterator/
• https://leetcode.com/problems/unique-binary-search-trees/
• https://leetcode.com/problems/serialize-and-deserialize-bst/
• https://leetcode.com/problems/binary-tree-right-side-view/
• https://leetcode.com/problems/binary-tree-level-order-traversal/
• https://leetcode.com/problems/binary-tree-level-order-traversal-ii/
• https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/

Dynamic programming

Easy

• https://leetcode.com/problems/maximum-subarray/
• https://leetcode.com/problems/fibonacci-number/
• https://leetcode.com/problems/climbing-stairs/
• https://leetcode.com/problems/min-cost-climbing-stairs/
• https://leetcode.com/problems/n-th-tribonacci-number/

Medium

• https://leetcode.com/problems/coin-change/
• https://leetcode.com/problems/minimum-falling-path-sum/
• https://leetcode.com/problems/minimum-cost-for-tickets/
• https://leetcode.com/problems/2-keys-keyboard/
• https://leetcode.com/problems/maximum-product-subarray/
• https://leetcode.com/problems/triangle/
• https://leetcode.com/problems/ones-and-zeroes/
• https://leetcode.com/problems/longest-arithmetic-subsequence/
• https://leetcode.com/problems/partition-equal-subset-sum/
• https://leetcode.com/problems/house-robber/
• https://leetcode.com/problems/decode-ways/
• https://leetcode.com/problems/word-break/
• https://leetcode.com/problems/edit-distance/
• https://leetcode.com/problems/longest-increasing-subsequence/

Graphs

Easy

• https://leetcode.com/problems/employee-importance/
• https://leetcode.com/problems/find-the-town-judge/

Medium

• https://leetcode.com/problems/course-schedule-ii/
• https://leetcode.com/problems/redundant-connection/
• https://leetcode.com/problems/surrounded-regions/
• https://leetcode.com/problems/accounts-merge/
• https://leetcode.com/problems/network-delay-time/
• https://leetcode.com/problems/is-graph-bipartite/
• https://leetcode.com/problems/find-eventual-safe-states/
• https://leetcode.com/problems/keys-and-rooms/
• https://leetcode.com/problems/possible-bipartition/
• https://leetcode.com/problems/most-stones-removed-with-same-row-or-column/
• https://leetcode.com/problems/rotting-oranges/
• https://leetcode.com/problems/number-of-operations-to-make-network-connected/

Additional questions

• https://leetcode.com/problems/longest-common-prefix/
• https://leetcode.com/problems/implement-trie-prefix-tree/

Random

• https://leetcode.com/explore/

Videos

Some long videos, to revise or study in one long stretch!

• Data Structures Easy to Advanced Course — Full Tutorial from a Google Engineer
• Introduction to Data Structures & Algorithms | Course Details & Prerequisites
• Algorithms Course — Graph Theory Tutorial from a Google Engineer