Two Pointers

Question 1

https://leetcode.com/problems/container-with-most-water/

Answer 1

Two Pointers - Converging (Sorted Array Target Sum)
Use two pointers moving towards each other to solve target sum problems

Question 2

https://leetcode.com/problems/3sum/description/

Answer 2

Two Pointers - Converging (Sorted Array Target Sum)
Use two pointers moving towards each other to solve target sum problems

Question 3

https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/description/

Answer 3

Two Pointers - Converging (Sorted Array Target Sum)
Use two pointers moving towards each other to solve target sum problems

Question 4

https://leetcode.com/problems/intersection-of-two-arrays/description/

Answer 4

Two Pointers - Converging (Sorted Array Target Sum)
Use two pointers moving towards each other to solve target sum problems

Question 5

https://leetcode.com/problems/boats-to-save-people/description/

Answer 5

Two Pointers - Converging (Sorted Array Target Sum)
Use two pointers moving towards each other to solve target sum problems

Question 6

https://leetcode.com/problems/squares-of-a-sorted-array/description/

Answer 6

Two Pointers - Converging (Sorted Array Target Sum)
Use two pointers moving towards each other to solve target sum problems

Question 7

https://leetcode.com/problems/linked-list-cycle/description/

Answer 7

Two Pointers - Fast & Slow (Cycle Detection)
Floyd’s cycle detection algorithm using fast and slow pointers

Question 8

https://leetcode.com/problems/happy-number/description/

Answer 8

Two Pointers - Fast & Slow (Cycle Detection)
Floyd’s cycle detection algorithm using fast and slow pointers

Question 9

https://leetcode.com/problems/find-the-duplicate-number/description/

Answer 9

Two Pointers - Fast & Slow (Cycle Detection)
Floyd’s cycle detection algorithm using fast and slow pointers

Question 10

https://leetcode.com/problems/is-subsequence/description/

Answer 10

Two Pointers - Fast & Slow (Cycle Detection)
Floyd’s cycle detection algorithm using fast and slow pointers

Question 11

https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/

Answer 11

Two Pointers - Fixed Separation (Nth Node from End)
Maintain fixed distance between pointers to find nth element from end

Question 12

https://leetcode.com/problems/middle-of-the-linked-list/

Answer 12

Two Pointers - Fixed Separation (Nth Node from End)
Maintain fixed distance between pointers to find nth element from end

Question 13

https://leetcode.com/problems/delete-the-middle-node-of-a-linked-list/description/

Answer 13

Two Pointers - Fixed Separation (Nth Node from End)
Maintain fixed distance between pointers to find nth element from end

Question 14

https://leetcode.com/problems/remove-duplicates-from-sorted-array/description/

Answer 14

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 15

https://leetcode.com/problems/remove-element/description/

Answer 15

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 16

https://leetcode.com/problems/sort-colors/description/

Answer 16

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 17

https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/description/

Answer 17

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 18

https://leetcode.com/problems/move-zeroes/description/

Answer 18

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 19

https://leetcode.com/problems/sort-array-by-parity/description/

Answer 19

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 19

https://leetcode.com/problems/string-compression/description/

Answer 19

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 20

https://leetcode.com/problems/move-pieces-to-obtain-a-string/description/

Answer 20

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 21

https://leetcode.com/problems/separate-black-and-white-balls/description/

Answer 21

Two Pointers - In-place Array Modification
Modify arrays in-place using two pointers technique

Question 22

https://leetcode.com/problems/backspace-string-compare/

Answer 22

Two Pointers - String Comparison with Backspaces
Handle string modifications with backspace operations

Question 23

https://leetcode.com/problems/crawler-log-folder/description/

Answer 23

Two Pointers - String Comparison with Backspaces
Handle string modifications with backspace operations

Question 24

https://leetcode.com/problems/longest-palindromic-substring/description/

Answer 24

Two Pointers - Expanding From Center (Palindromes) Find palindromes by expanding from center outwards

Question 25

https://leetcode.com/problems/palindromic-substrings/

Answer 25

Two Pointers - Expanding From Center (Palindromes) Find palindromes by expanding from center outwards

Question 26

https://leetcode.com/problems/reverse-words-in-a-string/description/

Answer 26

Two Pointers - String Reversal Reverse strings or parts of strings using two pointers

Question 27

https://leetcode.com/problems/reverse-string/description/

Answer 27

Two Pointers - String Reversal Reverse strings or parts of strings using two pointers

Question 28

https://leetcode.com/problems/reverse-vowels-of-a-string/

Answer 28

Two Pointers - String Reversal Reverse strings or parts of strings using two pointers

Question 29

https://leetcode.com/problems/reverse-string-ii/description/

Answer 29

Two Pointers - String Reversal Reverse strings or parts of strings using two pointers