Binary Search
Every comparison throws away half of what's left. Twenty questions beats a million.
5 lessons · ~49 min · free
By the end you can
- Feel why halving turns a million elements into twenty comparisons
- Write the classic template and know exactly why the loop terminates
- Find boundaries: first occurrence, last occurrence, lower and upper bound
- Search the answer space when there is no array at all
- Recognize monotonic structure, the real prerequisite for binary search
Lessons
Start the course- The power of throwing half away8 minThe guessing game, log₂ growth, and what sorted order actually buys you.
- The classic template11 minlo, hi, mid, and the loop condition, plus the two bugs that cause infinite loops.
- Boundaries: first and last11 minFirst occurrence, last occurrence, and the first-true picture that unifies them.
- Searching the answer space11 minNo array, no problem: binary search over candidate answers with a yes/no check.
- Spotting binary search problems8 minMonotonic structure in disguise, rotated arrays, and when halving simply doesn't apply.
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Practice it after
The final lesson links here too: real interview questions that test this pattern, in an editor with execution and AI feedback.