Tony's Log

Algorithms, Distributed System, Machine Learning
  博客园 :: 首页 :: 博问 :: 闪存 :: 新随笔 :: 联系 :: 订阅 订阅 :: 管理 ::

12 2017 档案

HackerRank "Repetitive K-Sums" !!!
摘要：Fancy, classic, STEP-BY-STEP Analysis strategy problem. Here is the approach: 1. Sort input arrays.. so sum[0] is a[0] * k, so we got a[0]2. Then who 阅读全文
posted @ 2017-12-30 03:55 Tonix 阅读(237) 评论(0) 推荐(0)

HackerRank "Bowling Pins" !!! [Game Theory]
摘要：Classic problem to learn Game Theory - an advanced one: how to identify sub-games.. For every move (hit 1\2 bins) on one continuous section, the origi 阅读全文
posted @ 2017-12-29 13:17 Tonix 阅读(254) 评论(0) 推荐(0)

HackerRank "Stone Division, Revisited"
摘要：DFS + memo. 阅读全文
posted @ 2017-12-29 09:09 Tonix 阅读(243) 评论(0) 推荐(0)

HackerRank "K Factorization"
摘要：Actually, it is a Greedy problem : ) 阅读全文
posted @ 2017-12-29 08:45 Tonix 阅读(133) 评论(0) 推荐(0)

HackerRank "Arithmetic Expressions" !
摘要：It is marked as Recursion on HR, but the optimal solution is DP. Step by step, discover internal mechanism. 阅读全文
posted @ 2017-12-28 13:45 Tonix 阅读(142) 评论(0) 推荐(0)

HackerRank "Poker Nim"
摘要：The trick of this problem is.. Adding 1+ coins to one pile, means nothing - you add one, then i just remove it.. so it is back to original game. So, b 阅读全文
posted @ 2017-12-27 12:29 Tonix 阅读(141) 评论(0) 推荐(0)

HackerRank "Nimble Game"
摘要：A simple NIM game in disguise: move 1 coin to one of previous slot, equals to removing.. Then no surprise, Sprague-Grundy theorem solves the problem. 阅读全文
posted @ 2017-12-27 11:55 Tonix 阅读(181) 评论(0) 推荐(0)

HackerRank "Misère Nim"
摘要：Another easy one solved by Sprague-Grundy theorem. Each pile is a sub-game, so you need to XOR SG value of all substates - since you can move # of 1 - 阅读全文
posted @ 2017-12-27 11:37 Tonix 阅读(144) 评论(0) 推荐(0)

HackerRank "Triangle Numbers"
摘要：A matter of OBSERVATION.. draw a triangle of parity, and watch. 阅读全文
posted @ 2017-12-27 08:46 Tonix 阅读(110) 评论(0) 推荐(0)

HackerRank "Flipping the Matrix"
摘要：Discrete thinking - Play & Observe! " you can move numbers in any quadrant at the following positions to [x][y]: [x][y] or // upper left quadrant [x][ 阅读全文
posted @ 2017-12-26 13:43 Tonix 阅读(196) 评论(0) 推荐(0)

HackerRank "Chessboard Game, Again!"
摘要：Another intuitive of application of Sprague-Grundy theorem. 阅读全文
posted @ 2017-12-26 13:18 Tonix 阅读(204) 评论(0) 推荐(0)

HackerRank "Tower Breakers, Again!"
摘要：An intuitive problem for learning & applying Sprague-Grudy theorem: https://zhuanlan.zhihu.com/maigo/20611132 Lesson learnt, in Sprague-Grundy theorem 阅读全文
posted @ 2017-12-26 11:12 Tonix 阅读(214) 评论(0) 推荐(0)

HackerRank - Yet Another Minimax Problem
摘要：The major trick is from another similar HR problem: subarray with max XOR: Build a binary tree bit by bit, and go from MSB to LSB, greedily. In this o 阅读全文
posted @ 2017-12-25 12:13 Tonix 阅读(243) 评论(0) 推荐(0)

HackerRank "Richie Rich"
摘要：Fun Greedy. My first thought was a DFS based solution... however the editorial provides a super neat 2-pass O(n) solution: Pass 1: if s[l] != s[r], ch 阅读全文
posted @ 2017-12-23 10:32 Tonix 阅读(124) 评论(0) 推荐(0)

HackerRank - String Construction
摘要：Over-thinking will not get you there though : ) The trick is QUITE easy: # of unique chars. 阅读全文
posted @ 2017-12-22 05:30 Tonix 阅读(128) 评论(0) 推荐(0)