LeetCode

The reposity is for recording submissions in LeetCode. Programing language is java and Scala.

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Array

tag easy

1. TwoSum
   map.containsKey()
2. Remove Duplicates From Sorted Array
   • two pointers
3. Remove Element
4. Search Insert Position
   • two pointers,binary search
5. Maximum Subarray
6. Plus One
   • immutable array of integer will be intialized with 0
7. Merge Sorted Array
8. Pascal's Triangle
   scala: unaccepted maybe linkedlist is the type to solve the problem
9. Pascal's Triangle2
   scala:unaccepted
10. Best Time to Buy and Sell Stock
    • CQ
    • Kadane's Algorithm: maximum subarray problem
11. Best Time to Buy and Sell Stock2
    • Peak Valley Approach
    • greedy algorithm is slower than the other solution
12. Two Sum2
    • two pointers
    • binary search : O(logn),defeat 99%
13. Majority Element
    • Mroove voting Algorithm
    • for extension: icebrug, element appears more than k times
14. Rotate Array
    bad solution
    • extra space;three times reversal;reserve
    • I consider that queue is the best data structure to solve the problem
15. Contains Duplicate
    scala:unaccepted
    • byte array: most fast
16. Contains Duplicate
    scala:unaccepted
    • set and sliding window
17. Move Zeroes
    • two pointers
    • while is faster than for loop
18. Third Maximum Number
    • the normal way O(logn)
    • priority queue: O(nlogn)
19. Find All Numbers Disappeared in an Array
    scala:unaccepted
20. Max Consecutive Ones
    • concise way has long runtime
21. K-diff pairs in an Array
    • sort then two pointers
    • map: map.entry map.keySet()
22. Array Partition
    • sort then ... nlogn
    • bucket sort, n. beats 98.97%. faster
23. Reshape the Matrix
    • common way

tag medium

1. Container With Most Water
   • two pointers
   • Math.max/min runtime seems slower than direct comparison