2014 年 7月随笔档案 - Tonix

LeetCode "Reverse Linked List II"

摘要：Just corner case..class Solution {public: ListNode *reverseBetween(ListNode *head, int m, int n) { if(m == n) return head; ListNode *... 阅读全文

posted @ 2014-07-31 08:06 Tonix 阅读(124) 评论(0) 推荐(0)

LeetCode "Unique Binary Search Trees II"

摘要：I fell in a deadloop, and didn't see the actual recursion pattern.Reference:http://fisherlei.blogspot.com/2013/03/leetcode-unique-binary-search-trees-... 阅读全文

posted @ 2014-07-31 07:19 Tonix 阅读(95) 评论(0) 推荐(0)

LeetCode "Combination Sum II"

摘要：The only difference with version I is: one number can only be used once:class Solution {public: vector > ret; struct Rec { Rec() : sum... 阅读全文

posted @ 2014-07-31 03:40 Tonix 阅读(106) 评论(0) 推荐(0)

LeetCode "Divide Two Integers"

摘要：A very interesting numeric problem. It involves a lot tricks.Linear search (by +\-) is not feasible - too slow. So binary search is a good idea. Also ... 阅读全文

posted @ 2014-07-29 12:25 Tonix 阅读(149) 评论(0) 推荐(0)

LeetCode "First Missing Positive"

摘要：Similar with "Longest Consecutive Sequence". Another usage to hashset.Take care of corner cases!class Solution {public: int firstMissingPositive(in... 阅读全文

posted @ 2014-07-28 12:27 Tonix 阅读(173) 评论(0) 推荐(0)

LeetCode "Clone Graph"

摘要：A BFS usage.class Solution {public: UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) { if (!node) return NULL; UndirectedGr... 阅读全文

posted @ 2014-07-28 11:49 Tonix 阅读(131) 评论(0) 推荐(0)

LeetCode "Decode Ways"

摘要：Similar with "Climb stairs" but with more restrictions.// Ref: http://yucoding.blogspot.com/2013/01/leetcode-question-26-decode-ways.htmlclass Solu... 阅读全文

posted @ 2014-07-28 08:25 Tonix 阅读(131) 评论(0) 推荐(0)

LeetCode "Combinations"

摘要：Typical recurrsion\DFS problem. Just take care of memory use.class Solution {public: vector> ret; void go(int currMaxN, int currK, int k, unorde... 阅读全文

posted @ 2014-07-28 06:12 Tonix 阅读(153) 评论(0) 推荐(0)

LeetCode "Populating Next Right Pointers in Each Node II"

摘要：Compared with I version, the tree could be incomplete. The only difference is that, we connect current node's child to next non-childrenless' node's f... 阅读全文

posted @ 2014-07-26 15:01 Tonix 阅读(145) 评论(0) 推荐(0)

LeetCode "Surrounded Regions"

摘要：Flood-Fill. BFS. But there's a trick. If we fill surrounded region directly, extra bookkeeping cost is needed - because we don't know whether that reg... 阅读全文

posted @ 2014-07-26 14:09 Tonix 阅读(189) 评论(0) 推荐(0)

LeetCode "Longest Consecutive Sequence"

摘要：Comparison-based sorting takes O(nlgn), so hashset is a good idea. After keeping records of all numbers in the hashset, you start checking each number... 阅读全文

posted @ 2014-07-25 01:14 Tonix 阅读(208) 评论(0) 推荐(0)

LeetCode "ZigZag Conversion"

摘要：Nothing to hard to think. Just take care of boundary conditions.class Solution {public: string convert(string s, int nRows) { if(s.empty() |... 阅读全文

posted @ 2014-07-23 12:54 Tonix 阅读(165) 评论(0) 推荐(0)

LeetCode "Copy List with Random Pointer"

摘要：Two passes: all pointer linking info will be recorded in 1st pass - to hashmap; 2nd pass recover the pointer relationship from hashmap.1A!class Soluti... 阅读全文

posted @ 2014-07-23 12:39 Tonix 阅读(149) 评论(0) 推荐(0)

LeetCode "Remove Nth Node From End of List"

摘要：Another Double pointer solution. 1A!class Solution {public: ListNode *removeNthFromEnd(ListNode *head, int n) { ListNode *p = NULL; ... 阅读全文

posted @ 2014-07-23 11:41 Tonix 阅读(120) 评论(0) 推荐(0)

LeetCode "Sqrt(x)"

摘要：2 solutions: bin-search and Newton iteration.class Solution {public: int _sqrt(long long tgt, long long i0, long long i1) { long long can... 阅读全文

posted @ 2014-07-23 05:41 Tonix 阅读(169) 评论(0) 推荐(0)

LeetCode "Construct Binary Tree from Inorder and Postorder Traversal"

摘要：Another textbook problem. We take back of postorder array as the current root, and then we can split the inorder array: 1st half for current right chi... 阅读全文

posted @ 2014-07-23 04:13 Tonix 阅读(142) 评论(0) 推荐(0)

LeetCode "Construct Binary Tree from Preorder and Inorder Traversal"

摘要：A collegiate textbook problem. Nothing special, but just take care of your memory use.class Solution {public: TreeNode *_buildTree(int pre[], int &... 阅读全文

posted @ 2014-07-23 03:29 Tonix 阅读(125) 评论(0) 推荐(0)

LeetCode "Flatten Binary Tree to Linked List"

摘要：Really interesting BST manipulation problem!class Solution {public: TreeNode *findConn(TreeNode *p) { TreeNode *pTmp = p; while (p... 阅读全文

posted @ 2014-07-22 13:04 Tonix 阅读(123) 评论(0) 推荐(0)

LeetCode "Unique Paths"

摘要：Now I believe thoughts leading to DP is brutal DFS.. DFS is brutal force enumeration, but that's too much and naive. We need pruning. So, DFS + Prunin... 阅读全文

posted @ 2014-07-22 12:12 Tonix 阅读(162) 评论(0) 推荐(0)

LeetCode "Sort Colors"

摘要：For the one pass solution... first I tried to build white\blue from red, but not working anyway. Then I referred someone' code, to build red\blue from... 阅读全文

posted @ 2014-07-22 11:31 Tonix 阅读(129) 评论(0) 推荐(0)

LeetCode "Max Points on a Line "

摘要：The first solution I figured out is O(n^3). I thought it must be O(n^2) to get max points on a line for a given point.. but after checking several art... 阅读全文

posted @ 2014-07-22 06:56 Tonix 阅读(141) 评论(0) 推荐(0)

LeetCode "Generate Parentheses"

摘要：DFS and using stack to validate candidates.class Solution {public: bool isValid(const string &s) { stack stk; for (int i = 0; i &... 阅读全文

posted @ 2014-07-21 11:02 Tonix 阅读(139) 评论(0) 推荐(0)

LeetCode "Plus One"

摘要：The trick is, we can work on a reversed vector - learnt from EPI.class Solution {public: vector plusOne(vector &digits) { std::reverse(digit... 阅读全文

posted @ 2014-07-21 10:32 Tonix 阅读(146) 评论(0) 推荐(0)

LeetCode "Symmetric Tree"

摘要：Recursive.class Solution { public: bool isSymmetric(TreeNode *pl, TreeNode *pr) { if (!pl && !pr) return true; if ((pl && !pr)... 阅读全文

posted @ 2014-07-21 10:19 Tonix 阅读(143) 评论(0) 推荐(0)

LeetCode "Merge Sorted Array"

摘要：My first reaction: move all A elements back by n positions, and start everything from A[0] and B[0]. But a smarter idea is to start everything from th... 阅读全文

posted @ 2014-07-21 10:18 Tonix 阅读(129) 评论(0) 推荐(0)

LeetCode "Balanced Binary Tree"

摘要：Another recursion problem.class Solution {public: int getHeight(TreeNode *p) { if (!p) return 0; int hL = 1; if (p->left) h... 阅读全文

posted @ 2014-07-21 07:38 Tonix 阅读(167) 评论(0) 推荐(0)

LeetCode "N-Queens II"

摘要：Classic recursion\pruning problem. We can use O(n) space: A[i] = j means [i,j] is occupied.class Solution {public: int ret; bool isValid(int *A,... 阅读全文

posted @ 2014-07-21 06:49 Tonix 阅读(121) 评论(0) 推荐(0)

LeetCode "Merge Two Sorted Lists"

摘要：Simply care about the boundary cases:class Solution {public: ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) { if (l1 && !l2) return l1;... 阅读全文

posted @ 2014-07-21 05:53 Tonix 阅读(160) 评论(0) 推荐(0)

LeetCode "Populating Next Right Pointers in Each Node"

摘要：Apparently BFS is the most obvious one.. but it is not that simple - only constant extra space is provided.Then the only strategy to take is recursion... 阅读全文

posted @ 2014-07-21 04:39 Tonix 阅读(268) 评论(0) 推荐(0)

LeetCode "Maximum Subarray"

摘要：Very classic problem. You can brush up your DP and Searching skills.DP:class Solution {public: int maxSubArray(int A[], int n) { // dp[i + 1... 阅读全文

posted @ 2014-07-21 04:19 Tonix 阅读(186) 评论(0) 推荐(0)

LeetCode "Unique Binary Search Trees"

摘要：Another recursion-style problem.1. Each count of sub-solution with a certain root should contribute to final count2. With a certain root, the num of l... 阅读全文

posted @ 2014-07-18 14:13 Tonix 阅读(113) 评论(0) 推荐(0)

LeetCode "Search Insert Position"

摘要：A simple 1D searching problem. Binary search of course.But.. STL has already done it for you:class Solution {public: int searchInsert(int A[], int ... 阅读全文

posted @ 2014-07-18 13:51 Tonix 阅读(94) 评论(0) 推荐(0)

LeetCode "Remove Element"

摘要：Since no order requirement, we can simply swap the target value to the last non-target-value in the array - if the last non-target-value is not behind... 阅读全文

posted @ 2014-07-18 13:35 Tonix 阅读(119) 评论(0) 推荐(0)

LeetCode "Climbing Stairs"

摘要：The best way to learn DP from DFS! Nice problem.My intuition is that it can be solved by DFS:class Solution {public: int climbStairs(int n) { ... 阅读全文

posted @ 2014-07-18 12:49 Tonix 阅读(159) 评论(0) 推荐(0)

LeetCode "Reorder List"

摘要：Not very hard to figure out the solution: splitting the list into 2 halves; reverse the 2nd half and interleave the two halves.But it takes some time ... 阅读全文

posted @ 2014-07-18 04:10 Tonix 阅读(146) 评论(0) 推荐(0)

LeetCode "Remove Duplicates from Sorted List"

摘要：The key of this problem is about details especially boundary conditions.class Solution {public: ListNode *deleteDuplicates(ListNode *head) { ... 阅读全文

posted @ 2014-07-18 01:01 Tonix 阅读(126) 评论(0) 推荐(0)

LeetCode "Validate Binary Search Tree"

摘要：This is to test your knowledge on BST and its traversal.Flatting BST into an array using in-order, and check that array. It is that simple:class Solut... 阅读全文

posted @ 2014-07-17 15:44 Tonix 阅读(143) 评论(0) 推荐(0)

LeetCode "Triangle"

摘要：This is the same asSPOJ #453. The best way to understand DP1A code:class Solution {public: int minimumTotal(vector > &triangle) { fo... 阅读全文

posted @ 2014-07-17 06:21 Tonix 阅读(144) 评论(0) 推荐(0)

LeetCode "Sum Root to Leaf Numbers"

摘要：A typical DFS usage, no big deal:class Solution {public: int dfs(TreeNode *p, int pval) { if( !p->left && !p->right ) { ... 阅读全文

posted @ 2014-07-17 05:27 Tonix 阅读(150) 评论(0) 推荐(0)

LeetCode "Single Number"

摘要：It is not a big deal at the first sight:https://oj.leetcode.com/problems/single-number/And my AC code is straightforward:#include using namespace std... 阅读全文

posted @ 2014-07-16 15:39 Tonix 阅读(145) 评论(0) 推荐(0)

POJ #1033 - Defragment

摘要：First, 写POJ的报告用毛英文啊...这道题思路不算难，主要参考了这里：http://www.cnblogs.com/damacheng/archive/2010/09/24/1833983.html讲得很清楚，但是代码有点复杂，我个人觉得不需要：循环情况可以当作非循环的一个特殊情况，简单处理... 阅读全文

posted @ 2014-07-16 12:04 Tonix 阅读(439) 评论(0) 推荐(0)

POJ #1011 - Sticks

摘要：This is really classic searching problem to solve. The key is pruning.(My reference:http://blog.csdn.net/lyy289065406/article/details/6647960)There ar... 阅读全文

posted @ 2014-07-15 06:27 Tonix 阅读(194) 评论(0) 推荐(0)

POJ #2411 - Mondriaan's Dream

摘要：Good reference:http://www.cppblog.com/sdfond/archive/2009/07/31/91761.htmlIt is a classic coverage\dp compression problem. Initially I thought of dp[i... 阅读全文

posted @ 2014-07-07 04:23 Tonix 阅读(179) 评论(0) 推荐(0)

POJ #1276 - Cash machine

摘要：I tried several solutions except the one fromhttp://love-oriented.com/pack/P03.html (wonderful resource to learn DP), but all failed with WA\TLE. Afte... 阅读全文

posted @ 2014-07-05 04:44 Tonix 阅读(183) 评论(0) 推荐(0)

POJ #1260 - Pearls

摘要：DP is, enumeration + pruning. If you can think of enumeration pattern of a problem, plus a recurrence relation later, you are there.Main ref:http://bl... 阅读全文

posted @ 2014-07-01 14:02 Tonix 阅读(123) 评论(0) 推荐(0)

Tony's Log

公告

07 2014 档案