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Episode 8 Binary Search

1 h 4 min · Java

Title card of Episode 8: Binary Search

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The complete guide to binary search for coding interviews, in Java. First the idea: halve the range with every look, the two templates (an exact value, and where a yes or no question flips), why the middle is lo + (hi − lo) / 2, what it saves, Java's built-in tools, and five traps. Then nine types, each worked as a small problem in full: examples, the brute force animated beside the running line of code, the complete code, every line explained, and the binary search the same way.

What you'll learn

  • How binary search halves the range, and why it's O(log n)
  • The exact-value template: lo <= hi with mid ± 1
  • The lower-bound template: lo < hi with hi = mid, for any question that flips once
  • Why (lo + hi) / 2 overflows, and the safe middle
  • Arrays.binarySearch, Collections.binarySearch, TreeSet floor and ceiling
  • First and last position with two lower bounds
  • Rotated sorted arrays: the minimum, and search, by asking which half is sorted
  • A sorted grid as one long line, and a peak without sorting
  • Binary search on the answer, and searching a key's timestamps

Chapters

  1. 0:00Intro
  2. 0:24Halve the range
  3. 0:59A question that flips once
  4. 1:54Template 1: an exact value
  5. 2:52Template 2: where it flips
  6. 3:44The overflow bug
  7. 4:17What binary search saves
  8. 4:47Binary search in Java
  9. 5:46Five traps
  10. 6:30Nine binary search types
  11. 7:12Type 1 · Find a number in a sorted array
  12. 12:47Type 2 · Where does it fit?
  13. 18:37Type 3 · First and last position
  14. 24:48Type 4 · Smallest number in a rotated array
  15. 30:59Type 5 · Search in a rotated array
  16. 37:07Type 6 · Search a sorted grid
  17. 43:01Type 7 · Find a peak
  18. 49:07Type 8 · Slowest eating speed
  19. 55:29Type 9 · Time based key-value store
  20. 1:01:38Spot the type
  21. 1:02:23Quiz: which type?
  22. 1:03:11Recap