Recognition signal
When should you think of Two Pointers?
A sorted order, opposing ends, or two sequences lets one pointer eliminate choices for the other.
15 worked problems
Two Pointers
Converge from both ends or chase in one pass. A sorted order, opposing ends, or two sequences lets one pointer eliminate choices for the other.
Core invariant
What must stay true?
Everything outside the active pointer range has already been classified.
Practice in a deliberate order
Starter
Build the template
Core
Recognize variations
What to learn in this cluster
- 01Opposite-end scans
- 02Fast and slow pointers
- 03Sorted k-sum reductions
All Two Pointers problems
15 of 15 walkthroughsNo matching problems. Try another title, tag, or difficulty.
- #26 Remove Duplicates from Sorted Arrayarray · two-pointersEasy
- #125 Valid Palindromestring · two-pointersEasy
- #242 Valid Anagramstring · hash-table · countingEasy
- #283 Move Zeroesarray · two-pointers · in-placeEasy
- #977 Squares of a Sorted Arraytwo-pointers · array · sortingEasy
- #11 Container With Most Waterarray · two-pointers · greedyMedium
- #15 3Sumarray · two-pointers · sortingMedium
- #16 3Sum Closestarray · two-pointers · sortingMedium
- #31 Next Permutationarray · two-pointersMedium
- #75 Sort Colorsarray · two-pointers · dutch-flagMedium
- #80 Remove Duplicates from Sorted Array IItwo-pointers · arraysMedium
- #88 Merge Sorted Arrayarray · two-pointersMedium
- #167 Two Sum II - Input Array Is Sortedarray · two-pointers · binary-searchMedium
- #881 Boats to Save Peopletwo-pointers · greedy · sortingMedium
- #42 Trapping Rain Waterarray · two-pointersHard
Continue the cluster