DESCRIPTION

Just a repo me practising DSA problems I used neetcode roadmap

PROBLEMS (Arrays and Hashing)

1. duplicate in array (set) mySolution
2. is Anagram (hmap, store character count) mySolution
3. two sums (hmap, key = ele, value = index, x + y = target i,e x = target - y) mySolution
4. k most frequent element (hmap , key = num, value = frequency, sorted bucket algo) mySolution
5. String Encode and Decode (attached length of string before actual string) mySolution
6. Products of Array Discluding Self (maintained product of left and right of an element) mySolution
7. longest consecutive sequence (set , if num - 1 is not in the set then num is the new sequence) mySolution

PROBLEMS (Two Pointers)

8. is palindrome (compare two pointer one from start and one from end, skip if the byte/character is not alphanumeric) mySolution
9. Two Sum II - Input Array Is Sorted (array is sorted is ASC, left and right pointers) mySolution
10. Three Integer Sum (sort the array, positive sum cant be zero, impelement two sum(two pointer) logic in the inner loop) mySolution
11. Maximum Water Container ( used two pointer left and right , index will be the width and element is the actual height of bar, and find the area = min(height[left], height[right]) * (right - left) ) mySolution

PROBLEMS (Stack)

12. Validate Parentheses mySolution
13. Minimum Stack (maintained a minimum and normal stack, used minimum stack to retrive the minimum value of the stack) mySolution
14. Evaluate Reverse Polish Notation mySolution
15. Daily Temperatures (used stack to store the index of an temperatures, just start from reverse and think) mySolution

PROBLEMS (Binary Search)

16. Binary Search mySolution
17. Search 2D Matrix (find potential row by doing BS on first column and again do BS on that potential row) mySolution
18. Koko Eating Bananas (min and max speed of koko is 1 and max(piles), do that BS on that range and check againt the totaltime at that mid rate) mySolution
19. Find Minimum in Rotated Sorted Array (min elemnet will be always less than left and right) mySolution
20. Find Target in Rotated Sorted Array (first check target == mid, if not find the sorted and unsorted subarray and then check wether that target is fit on the sorted or unsorted subarray) mySolution
21. Time Based Key-Value Store (since set timestamp is in increasing order, do BS) mySolution

PROBLEMS (Window Sliding)

22. Maximum Average Subarray I (subtract the previous ele in left pointer and add the new element to the previous sum) mySolution
23. Buy and Sell Crypto (dynamic size window) mySolution
24. Longest Substring Without Duplicates (dynamic size window and set for checking repeated character) mySolution
25. Minimum Window Substring (use left ptr to find the minimum sub string and right ptr to find that WS that contains the target sub string characters) mySolution
26. Sliding Window Maximum (monotonic queue) mySolution

PROBLEMS (Link List)

27. Reverse a singly linked list mySolution
28. Merge Two sorted singly linked list (used two pointer and apply the same logic of merging two sorted array) mySolution
29. Reorder singly linked list (midpoint, reversed second half, merged alternately) mySolution
30. Remove Node From End of Linked List (first -pointer 𝑛 steps ahead and second points to the node just before the nth node we need removed, used dummy node for edge case) mySolution
31. Add Two Numbers mySolution
32. Linked list cycle detection mySolution
33. Find the duplicate (array problem but need slow and fast pointer used in Linked List) mySolution