随笔档案「2014年8月」 - Tonix

HackerRank "Maximizing XOR"

摘要：A natural thought is brutal-force. But as you may have already thought of, there must be a smarter one. And yes there is.Think like this: XOR gives yo... 阅读全文

posted @ 2014-08-28 12:02 Tonix 阅读(268) 评论(0) 推荐(0)

LeetCode 1st Round Done

摘要：Welcome, T******7! You have solved151 / 151problems.It is only the first step... 阅读全文

posted @ 2014-08-26 14:15 Tonix 阅读(135) 评论(0) 推荐(0)

LeetCode "Word Ladder II"

摘要：Man it took me numerous submissions to get AC, and I referred to this link:http://yihuad.blogspot.com/2013/11/word-ladder-ii-leetcode.htmlIdea is pret... 阅读全文

posted @ 2014-08-24 10:48 Tonix 阅读(190) 评论(0) 推荐(0)

LeetCode "Maximal Rectangle"

摘要：My intuition is flood-fill the BFS solution, which is O(n^4); and then I figured out a DP solution which is O(n^4).. So I googled some hints: it can b 阅读全文

posted @ 2014-08-24 08:03 Tonix 阅读(147) 评论(0) 推荐(0)

LeetCode "Scramble String"

摘要：I have to admit that I'm still an algorithm rookie: in front of a problem, I got lost on what the nature of the problem is.. usually I made everything... 阅读全文

posted @ 2014-08-24 07:23 Tonix 阅读(166) 评论(0) 推荐(0)

LeetCode "Edit Distance"

摘要：A really classic 2D DP problem. And I'm glad that I figured out the transfer function without checking any other resources.After that, everything is s... 阅读全文

posted @ 2014-08-22 14:57 Tonix 阅读(151) 评论(0) 推荐(0)

LeetCode "Gas Station" - TO BE REVISED

摘要：First I thought of a DP solution.. but TLE. So there must be a O(n). I thought of Mono-Queue.. but looks too complex.So what is the naive solution? O(... 阅读全文

posted @ 2014-08-21 13:23 Tonix 阅读(173) 评论(0) 推荐(0)

LeetCode "Median of Two Sorted Arrays"

摘要：1A! We get median of each array and compare them, then we know which half should be disguarded and how many should be disguarded.class Solution {publi... 阅读全文

posted @ 2014-08-21 12:09 Tonix 阅读(164) 评论(0) 推荐(0)

LeetCode "Distinct Subsequences" - TO BE REVISED

摘要：A classic and representative DP problem. To be revised later. Quite a few interesting details to think about.class Solution {public: int numDistinc... 阅读全文

posted @ 2014-08-21 11:28 Tonix 阅读(143) 评论(0) 推荐(0)

LeetCode "Permutation Sequence"

摘要：1A! This is actually a basic question in Combinatorics: if at digit[k] = n, it contributes (k-1)! * n to the targeted index.class Solution {public: ... 阅读全文

posted @ 2014-08-19 13:26 Tonix 阅读(152) 评论(0) 推荐(0)

懒

摘要：找到自己切题的主要障碍了：试图刚读完题就foresee到最后的solution，其实就是妄图利用比较省事的感性直接超越逻辑推导的理性：其实就是懒。超验感性实际上是建立在大量理性的思考与实践上的。这话不是我说的，出自一位顶尖数学家之口。更别说偶了。阅读全文

posted @ 2014-08-19 12:40 Tonix 阅读(151) 评论(0) 推荐(0)

LeetCode "Linked List Cycle II"

摘要：Nothing but admire: http://fisherlei.blogspot.com/2013/11/leetcode-linked-list-cycle-ii-solution.htmlclass Solution {public: ListNode *detectCycle(... 阅读全文

posted @ 2014-08-19 12:36 Tonix 阅读(146) 评论(0) 推荐(0)

LeetCode "Best Time to Buy and Sell Stock III"

摘要：Refer: http://blog.unieagle.net/2012/12/05/leetcode%E9%A2%98%E7%9B%AE%EF%BC%9Abest-time-to-buy-and-sell-stock-iii%EF%BC%8C%E4%B8%80%E7%BB%B4%E5%8A%A8%... 阅读全文

posted @ 2014-08-19 11:42 Tonix 阅读(183) 评论(0) 推荐(0)

LeetCode "4Sum"

摘要：Similar strategy could be applied to 4Sum, as 2sum to 3sum, but that'll be O(n^3). Instead of 3 + 1, we can also divide it into 2 + 2. So the problem ... 阅读全文

posted @ 2014-08-18 12:23 Tonix 阅读(191) 评论(0) 推荐(0)

LeetCode "3Sum closest"

摘要：Simply a variation of 3Sum:class Solution {public: int threeSumClosest(vector &num, int target) { int ret = 99999999999; std::sort(nu... 阅读全文

posted @ 2014-08-18 10:39 Tonix 阅读(141) 评论(0) 推荐(0)

LeetCode "3Sum"

摘要：Now that you've solved 2sum, 3sum can be easily converted as 2sum.Also please note the while loops for i1 and i2: they are to make sure no duplicates.... 阅读全文

posted @ 2014-08-18 10:12 Tonix 阅读(153) 评论(0) 推荐(0)

LeetCode "Container With Most Water"

摘要：O(n^2) is a naive solution. As rule of thumb, there must be O(n) soluion. Yes - Greedy.We assume widest container contains the most water, greedily, b... 阅读全文

posted @ 2014-08-16 14:38 Tonix 阅读(140) 评论(0) 推荐(0)

Data Structures

摘要：-!5. Trie\Suffix Tree:http://blog.csdn.net/v_july_v/article/details/6897097 Trie: think about how you used King Dict by typing; Suffix Tree: all suff... 阅读全文

posted @ 2014-08-16 14:06 Tonix 阅读(214) 评论(0) 推荐(0)

LeetCode "Sudoku Solver"

摘要：Simply DFS + Backtrace, as N-Queenclass Solution {public: vector> rows; vector> cols; vector>> subboxHm; bool isValid(char c, int i, int j... 阅读全文

posted @ 2014-08-16 06:34 Tonix 阅读(147) 评论(0) 推荐(0)

LeetCode "Valid Sudoku"

摘要：Here another memory for speed implementation:class Solution {public: bool isValidSudoku(vector > &board) { size_t row_cnt = board.size(); ... 阅读全文

posted @ 2014-08-15 12:20 Tonix 阅读(157) 评论(0) 推荐(0)

LeetCode "Candy" - from skill to thought

摘要：Main reference: http://zhaohongze.com/wordpress/2013/12/10/leetcode-candy/I was confused by the constraint on BOTH sides of an element. Strategy is: s... 阅读全文

posted @ 2014-08-15 10:13 Tonix 阅读(247) 评论(0) 推荐(0)

LeetCode "Binary Tree Maximum Path Sum"

摘要：http://yucoding.blogspot.com/2012/12/leetcode-question-13-binary-tree.htmlUsually for tree problems, it is either recursion or traversal. For this one... 阅读全文

posted @ 2014-08-15 08:11 Tonix 阅读(117) 评论(0) 推荐(0)

LeetCode "Largest Rectangle in Histogram" - TRICKY MONO-QUEUE

摘要：I got a DP solution first which is O(n^2). Apparently it is not a optimized one - think about: it is linear value space. There must be O(n) solution.A... 阅读全文

posted @ 2014-08-15 04:48 Tonix 阅读(318) 评论(0) 推荐(0)

LeetCode "LRU Cache"

摘要：1A. It is a design problem actually. It tests your ability to connect your knowledge of data structures & algorithms, with real world problems.class L... 阅读全文

posted @ 2014-08-14 08:46 Tonix 阅读(169) 评论(0) 推荐(0)

LeetCode "Text Justification"

摘要：Just take care of corner cases!class Solution {public: vector fullJustify(vector &words, int L) { vector ret; int startInx = 0; ... 阅读全文

posted @ 2014-08-13 09:40 Tonix 阅读(145) 评论(0) 推荐(0)

LeetCode "Word Ladder" - TRICKY

摘要：It is not as easy as I thought it to be, mostly because of time\space limitation. And actually that's the punch line of this problemMy intuition was D... 阅读全文

posted @ 2014-08-13 07:30 Tonix 阅读(163) 评论(0) 推荐(0)

LeetCode "Minimum Window Substring" - STAR

摘要：Main reference:http://zhaohongze.com/wordpress/2014/01/04/leetcode-minimum-window-substring/The ART of counting. So difficult and beautiful problem. I... 阅读全文

posted @ 2014-08-12 11:12 Tonix 阅读(170) 评论(0) 推荐(0)

LeetCode "Regular Expression Matching"

摘要：It took me numerous submissions to get AC.... until I checked this article:http://leetcode.com/2011/09/regular-expression-matching.htmlVery clean idea... 阅读全文

posted @ 2014-08-12 05:05 Tonix 阅读(152) 评论(0) 推荐(0)

LeetCode "Anagrams"

摘要：Problem is, find all values that share the same key value. Similar as another LeetCode problem, hashmap is a good choice.http://yucoding.blogspot.com/... 阅读全文

posted @ 2014-08-11 12:56 Tonix 阅读(163) 评论(0) 推荐(0)

LeetCode "Interleaving String"

摘要：I briefly took a look at:http://yucoding.blogspot.com/2013/01/leetcode-question-27-interleaving-string.htmlAnd I got 1A :)This is the best problem to ... 阅读全文

posted @ 2014-08-11 11:57 Tonix 阅读(158) 评论(0) 推荐(0)

LeetCode "Palindrome Partition II" - Double DP

摘要：A so juicy and interesting problem! Recommend to everyone!A final solution may not jump into your mind immediately, of course, DP is not a trivial top... 阅读全文

posted @ 2014-08-10 14:05 Tonix 阅读(309) 评论(0) 推荐(0)

LeetCode "Longest Substring Without Repeating Characters"

摘要：What a juicy problem to solve :) My intuition is DP, but failed with TLE. Then I referred to:http://leetcode.com/2011/05/longest-substring-without-rep... 阅读全文

posted @ 2014-08-09 06:42 Tonix 阅读(141) 评论(0) 推荐(0)

LeetCode "Wildcard Matching"

摘要：Here is the most elegant code I've seen to this problem:http://yucoding.blogspot.com/2013/02/leetcode-question-123-wildcard-matching.htmlSimply wow. I... 阅读全文

posted @ 2014-08-09 04:02 Tonix 阅读(210) 评论(0) 推荐(0)

LeetCode "Best Time to Buy and Sell Stock II"

摘要：No limit to transaction count, so it is a recursive sum calculation. Take care of boundary condition.class Solution {public: int maxProfit(vector &... 阅读全文

posted @ 2014-08-08 14:31 Tonix 阅读(162) 评论(0) 推荐(0)

LeetCode\EPI "Best Time to Buy and Sell Stock"

摘要：Also the very first problem on EPI.class Solution {public: int maxProfit(vector &prices) { size_t len = prices.size(); if (len = pric... 阅读全文

posted @ 2014-08-08 14:20 Tonix 阅读(162) 评论(0) 推荐(0)

LeetCode "Substring with Concatenation of All Words"

摘要："that are all of the same length" is the key. This statement makes everything much simpler. And, please take care that L may contain duplicated string... 阅读全文

posted @ 2014-08-08 13:54 Tonix 阅读(123) 评论(0) 推荐(0)

LeetCode "Word Break II"

摘要：Since it is a "return all" problem, we can use DFS. But brutal DFS got a TLE. So pruning is required.I referred tohttp://fisherlei.blogspot.com/2013/1... 阅读全文

posted @ 2014-08-08 08:09 Tonix 阅读(188) 评论(0) 推荐(0)

LeetCode "Word Break"

摘要：My first solution was DFS - TLE. Apparently, DFS with TLE usually means DP.1D DP + Rolling Array:class Solution {public: bool wordBreak(string s, u... 阅读全文

posted @ 2014-08-08 07:14 Tonix 阅读(182) 评论(0) 推荐(0)

Some thoughts..

摘要：I think it is natural for an algorithm rookie that when facing a challenging problem, a rookie may fall into her\his algorithm dictionary - she focuse... 阅读全文

posted @ 2014-08-06 13:51 Tonix 阅读(155) 评论(0) 推荐(0)

LeetCode "Longest Valid Parentheses"

摘要：Your intuition would tell you that there's a O(n) solution. Actually it is another stack-based problem to solve.class Solution {public: struct Rec ... 阅读全文

posted @ 2014-08-06 13:40 Tonix 阅读(157) 评论(0) 推荐(0)

LeetCode "Valid Number"

摘要：It took me +20 submissions to get AC... Actually the statement is too vague. I would rather ask for requirements f2f.Apparently the code below can be ... 阅读全文

posted @ 2014-08-06 07:39 Tonix 阅读(142) 评论(0) 推荐(0)

LeetCode "Longest Palindromic Substring" - 1D DP

摘要：2D DP is an intuitive solution of course, but I got an MLE error, so I simplified it into a 1D DP:class Solution {public: void goDp(vector &dp, int... 阅读全文

posted @ 2014-08-06 05:56 Tonix 阅读(167) 评论(0) 推荐(0)

LeetCode "Reverse Nodes in k-Group"

摘要：Another list manipulation problem.class Solution {public: ListNode *reverseKGroup(ListNode *head, int k) { if (!head) return head; if... 阅读全文

posted @ 2014-08-06 04:46 Tonix 阅读(159) 评论(0) 推荐(0)

LeetCode "Recover Binary Search Tree"

摘要：An example of in-order traversal application. My intuition is that, we have to serialize it into an array and check, but in-order traversal does exact... 阅读全文

posted @ 2014-08-05 01:47 Tonix 阅读(145) 评论(0) 推荐(0)

LeetCode "Word Search"

摘要：DFS + Backtrace + Pruningclass Solution {public: vector > visited; bool checkPos(vector > &board, char c, int currX, int currY) { ... 阅读全文

posted @ 2014-08-04 14:43 Tonix 阅读(192) 评论(0) 推荐(0)

LeetCode "Minimum Path Sum" - 2D DP

摘要：An intuitive 2D DP: dp[i][j] = min(grid[i-1][j-1] + dp[i-1][j], grid[i-1][j-1] + dp[i][j+1])class Solution {public: int minPathSum(vector > &grid) ... 阅读全文

posted @ 2014-08-03 07:30 Tonix 阅读(196) 评论(0) 推荐(0)

LeetCode "Remove Duplicates from Sorted List II"

摘要：Corner cases!class Solution {public: ListNode *deleteDuplicates(ListNode *head) { if (!head) return head; if (!head->next) return hea... 阅读全文

posted @ 2014-08-03 07:04 Tonix 阅读(174) 评论(0) 推荐(0)

LeetCode "Partition List"

摘要：Nothing special. A typical list manipulation problem.class Solution {public: ListNode *partition(ListNode *head, int x) { if (!head) return ... 阅读全文

posted @ 2014-08-03 06:39 Tonix 阅读(134) 评论(0) 推荐(0)

LeetCode "Restore IP Addresses"

摘要：It is all about corner cases.class Solution {public: vector retv; bool isValid(string &sub) { unsigned cnt = sub.length(); if (... 阅读全文

posted @ 2014-08-02 11:07 Tonix 阅读(184) 评论(0) 推荐(0)

LeetCode "Permutations"

摘要：Lexicographicallyalgorithms:1. Iterate array from back to front, and find the first decreasing point: 1,2,4,3 -- 42. Iterate array from back to front,... 阅读全文

posted @ 2014-08-02 03:42 Tonix 阅读(142) 评论(0) 推荐(0)

LeetCode "Sort List"

摘要：First I implemented it by QuickSort, but got a TLE:class Solution {public: struct Pair { Pair(ListNode *pS, ListNode *pE) : pStart(pS), p... 阅读全文

posted @ 2014-08-02 03:19 Tonix 阅读(148) 评论(0) 推荐(0)

LeetCode "Jump Game II"

摘要：Greedy, Greedy, Greedy.. It is all about maximum interval update.One trick is, we start looping over each element from the one nearest to end to farth... 阅读全文

posted @ 2014-08-01 12:07 Tonix 阅读(129) 评论(0) 推荐(0)

LeetCode "Jump Game"

摘要：A simulation problem. We simple walk through all reachable items until we cannot proceed.class Solution {public: bool canJump(int A[], int n) { ... 阅读全文

posted @ 2014-08-01 11:11 Tonix 阅读(115) 评论(0) 推荐(0)

LeetCode "Pow(x,n)"

摘要：Next time you see a numeric problem has a too straightforward solution, think about optimized one.Like this one: recursion\iteration is tooo slow. SoD... 阅读全文

posted @ 2014-08-01 05:09 Tonix 阅读(162) 评论(0) 推荐(0)

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08 2014 档案