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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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