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Array Patterns

Master the array patterns interviews love: two pointers, sliding window, prefix sums, intervals, and matrix tricks.

Islands
5
Lessons
45
Exercises
282
Complete codeDebugCode orderFill blankMultiple choiceTapTrace
  1. Island 1

    Two Pointers

    1. When Two Pointers Apply5 exercises, 4 min
    2. Two Sum II6 exercises, 6 min
    3. Container With Most Water6 exercises, 6 min
    4. Move Zeroes6 exercises, 6 min
    5. 3Sum6 exercises, 7 min
    6. Sort Colors6 exercises, 6 min
    7. Two Pointers CheckpointCheckpoint6 exercises, 6 min
    8. Two Pointers ReviewReview7 exercises, 6 min
    9. Boss: Trapping Rain WaterBoss8 exercises, 10 min
  2. Island 2

    Sliding Window

    1. When a Window Slides5 exercises, 4 min
    2. Best Time to Buy and Sell Stock6 exercises, 6 min
    3. Maximum Average Subarray6 exercises, 6 min
    4. Longest Substring Without Repeats6 exercises, 6 min
    5. Permutation in String6 exercises, 6 min
    6. Max Consecutive Ones III6 exercises, 6 min
    7. Sliding Window CheckpointCheckpoint6 exercises, 6 min
    8. Sliding Window ReviewReview7 exercises, 6 min
    9. Boss: Minimum Window SubstringBoss8 exercises, 10 min
  3. Island 3

    Prefix Sum

    1. Precompute the Running Total5 exercises, 4 min
    2. Running Sum of an Array6 exercises, 5 min
    3. Range Sum in O(1)6 exercises, 6 min
    4. Find Pivot Index6 exercises, 5 min
    5. Product of Array Except Self6 exercises, 6 min
    6. Contiguous Array7 exercises, 6 min
    7. Prefix Sum CheckpointCheckpoint6 exercises, 6 min
    8. Prefix Sum ReviewReview7 exercises, 6 min
    9. Boss: Subarray Sum Equals KBoss8 exercises, 10 min
  4. Island 4

    Intervals

    1. Thinking on a Number Line5 exercises, 4 min
    2. Summary Ranges6 exercises, 5 min
    3. Insert Interval6 exercises, 6 min
    4. Interval List Intersections6 exercises, 6 min
    5. Non-overlapping Intervals6 exercises, 6 min
    6. Minimum Arrows to Burst Balloons6 exercises, 6 min
    7. Intervals CheckpointCheckpoint6 exercises, 6 min
    8. Intervals ReviewReview7 exercises, 6 min
    9. Boss: Merge IntervalsBoss8 exercises, 10 min
  5. Island 5

    Matrices

    1. Working in Two Dimensions5 exercises, 4 min
    2. Transpose a Matrix6 exercises, 5 min
    3. Matrix Diagonal Sum6 exercises, 5 min
    4. Set Matrix Zeroes6 exercises, 6 min
    5. Spiral Matrix7 exercises, 6 min
    6. Valid Sudoku6 exercises, 6 min
    7. Matrices CheckpointCheckpoint6 exercises, 6 min
    8. Matrices ReviewReview7 exercises, 6 min
    9. Boss: Rotate ImageBoss8 exercises, 10 min
AlgoFox Pro

Array Patterns is part of AlgoFox Pro

You can read the whole course outline here. The exercises are in the app, along with your streak, your mistake review, and the progress that carries across your devices.

Pro starts with a 3 day free trial. The app store decides who is eligible for an introductory offer, and a lapsed subscription does not get another one.

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