Tonix - 博客园

HackerRank - "Sam and sub"

摘要： Brutal-force solution is not hard to think about. But linear space input usually indicates O(n) DP solution.State design: dp[i]: total sum until index... 阅读全文

posted @ 2015-07-15 13:14 Tonix 阅读(393) 评论(0) 推荐(0)

LeetCode "Delete Node in a Linked List"

摘要： An interview problem I encountered years ago.. 1ACclass Solution {public: void deleteNode(ListNode* node) { if(!node) return; Lis... 阅读全文

posted @ 2015-07-15 09:10 Tonix 阅读(143) 评论(0) 推荐(0)

HackerRank - "Mr K marsh"

摘要： My first thought made it unnecessarily difficult. Well, the correct solution falls into a typical pattern: use DP to calc cumulative results of each c... 阅读全文

posted @ 2015-07-14 05:02 Tonix 阅读(516) 评论(0) 推荐(0)

LeetCode "Lowest Common Ancestor of a BST"

摘要： First please note, it is BST. So it is about value compare.class Solution {public: TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, Tree... 阅读全文

posted @ 2015-07-11 06:27 Tonix 阅读(195) 评论(0) 推荐(0)

HackerRank "Hamming Distance"

摘要： A typical bucketing strategy, but it is probably the most complex one..Basically I refer tothissubmission. 阅读全文

posted @ 2015-07-10 13:16 Tonix 阅读(299) 评论(0) 推荐(0)

LeetCode "Palindrome Linked List"

摘要： O(n) time O(n) space solution using stack:class Solution {public: bool isPalindrome(ListNode* head) { if (!head || !head->next) return t... 阅读全文

posted @ 2015-07-10 10:13 Tonix 阅读(136) 评论(0) 推荐(0)

LeetCode "Number of Digit One"

摘要： Marked as mathematics problem, but if you are able to divide 1s into several cases, the AC code becomes natural.class Solution { unordered_map memo... 阅读全文

posted @ 2015-07-08 14:45 Tonix 阅读(193) 评论(0) 推荐(0)

HackerRank - "Equal"

摘要： First I was stuck at how to represent state of "add all except i".. but after checking editorial, it is simply inverted Coin Change problem..#include ... 阅读全文

posted @ 2015-07-07 05:38 Tonix 阅读(377) 评论(0) 推荐(0)

LeetCode "Implement Queue using Stacks"

摘要： Very similar as "Implement Stack using Queues".class Queue { stack _s0; stack _s1; int _front; public: // Push element x to the back of... 阅读全文

posted @ 2015-07-07 04:45 Tonix 阅读(181) 评论(0) 推荐(0)

LeetCode "Power of Two"

摘要： Just one line. Bit-wise ops:class Solution {public: bool isPowerOfTwo(int n) { return (n > 0) && (n & (n - 1)) == 0; }}; 阅读全文

posted @ 2015-07-06 07:35 Tonix 阅读(138) 评论(0) 推荐(0)

HackerRank - "Red John is Back"

摘要： 1AC. 1D DP + Sieving#include #include #include #include #include #include #include #include #include #include #include using namespace std;int ways(in... 阅读全文

posted @ 2015-07-03 06:58 Tonix 阅读(210) 评论(0) 推荐(0)

HackerRank - "Grid Walking"

摘要： Good one.. marked as DP, so I was striking to work out a DP formula... well, not all DP have a formula - one type of DP is called memorized search: th... 阅读全文

posted @ 2015-07-02 14:08 Tonix 阅读(830) 评论(0) 推荐(0)

LeetCode "Kth Smallest Element in a BST"

摘要： Simply to utilize BST's property. The two-pass code below can be extended to support frequent insert\delete.struct SNode{ SNode(int rcnt) : cnt(rcn... 阅读全文

posted @ 2015-07-02 09:45 Tonix 阅读(150) 评论(0) 推荐(0)

HackerRank - "Stock Maximize"

摘要： First I thought it should be solved using DP, and I gave a standard O(n^2) solution:#include #include #include #include using namespace std;#define RE... 阅读全文

posted @ 2015-07-01 07:10 Tonix 阅读(327) 评论(0) 推荐(0)

HackerRank - "The Coin Change Problem"

摘要： If coin order matters, that is, each sequence is unique, the DP function is simple enough to make it 1D DP. But key is that order DOESN'T matter, so w... 阅读全文

posted @ 2015-06-30 05:22 Tonix 阅读(467) 评论(0) 推荐(0)

LeetCode "Roman to Integer"

摘要： class Solution {public: int romanToInt(string s) { std::unordered_map hm; hm['M'] = 1000; hm['D'] = 500; hm['C'] = ... 阅读全文

posted @ 2015-06-30 04:48 Tonix 阅读(145) 评论(0) 推荐(0)

LeetCode "Integer to Roman"

摘要： char dict[] = {'I', 'V', 'X', 'L', 'C', 'D', 'M'};class Solution { public: string pattern(int v, int level) { int offset = int(log10(l... 阅读全文

posted @ 2015-06-30 04:39 Tonix 阅读(134) 评论(0) 推荐(0)

LeetCode "Majority Element II"

摘要： Similar as "Majority Element". There are at most 2 such elements, for > floor(n/3), and every non-hit element will decrease count of EACH hit element.... 阅读全文

posted @ 2015-06-29 23:21 Tonix 阅读(136) 评论(0) 推荐(0)

HackerRank - "Xor subsequence"

摘要： The Editorial provides a Fast Fourier Transformation solution O(nlgn)... which is too maths for me. In the leaderboard, I found a not-that-fast O(n^2)... 阅读全文

posted @ 2015-06-25 14:14 Tonix 阅读(321) 评论(0) 推荐(0)

HackerRank - "XOR key"

摘要： New techniques learnt: Trie can be used for some XOR problems. The basic idea: we build a MSB->LSB prefix Trie of all numbers; then query greedily: fi... 阅读全文

posted @ 2015-06-25 12:35 Tonix 阅读(346) 评论(0) 推荐(0)

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