leetcode

Recording my solution about leetcode. Most language is JavaScript,with very small part is Java.

Stage-1

• Finish easy level at 2016/8/16.
• 81 / 385 questions solved.

Feelings of Stage-1:

• 1. Easy level focus on AC result, not very concerned about time complexity and space complexity.This means my some solutions maybe used Burte-Force thought.Some problem inspects divide-and-conquer, recursion, Reduce and Conquer Method(e.g. binary divide), simple dynamic programming(dp).
• 2. Basic data structure: Array, Stack, Tree, Map, Set.
• 3. Easy level covers following aspects:
  • String
    • some implementations of built-in functions.For example,indexOf(), parseInt()/parseFloat() ,etc.
    • insert, delete, update, query
  • Array
    • basic operation about built-in function.indexOf, lastIndexOf(), push(), pop(), sort, slice,forEach(), concat(), join(), reverse(), shift(), unshift(), splice()
  • Set
    • use its Non-repetitive nature to remove duplicate.For example, pass parameters to its constructor like var set = new Set(nums);
  • Map
    • use hash to save/cache key-values items.It is very helpful in some problem if I want to built some mapping relation of strings.
  • Stack
    • baisc operation such as push, pop, peek, size(), isEmpty().
    • use stack to check whether parentheses is valid.
  • linked list
    • basic operation such as: query a certain node's value, remove/insert/update a node(maybe can't change node's value, only node itself can be changed)
    • reverse and its derivation
  • Tree
    • a large part of the easy level problems are related to tree.Tree traversal(inOrder,preOrder,postOrder),the depth of tree,BST related(to find a certain value).
    • many solutions are recursive for code clean,but its efficiency sometimes will be slower than iteration(e.g. fibonacci sequence)