Leetcode - 随笔分类(第15页) - neverlandly

Leetcode: Combination Sum IV && Summary: The Key to Solve DP

摘要：DP 解法： the key to solve DP problem is to think about how to create overlap, how to re-solve subproblems（怎么制造复用） Bottom up dp: Better Solution(Bottom-u 阅读全文

posted @ 2016-11-28 11:40 neverlandly 阅读(328) 评论(0) 推荐(0)

Leetcode: Wiggle Subsequence

摘要：DP solution is O(N^2), better way is greedy Now for explanation, we take example series:2,1,4,5,6,3,3,4,8,4 First we check if the series is starting a 阅读全文

posted @ 2016-11-28 10:26 neverlandly 阅读(533) 评论(0) 推荐(0)

Leetcode: Guess Number Higher or Lower II

摘要：Clarification of the problem: https://discuss.leetcode.com/topic/68252/clarification-on-the-problem-description-problem-description-need-to-be-updated 阅读全文

posted @ 2016-11-28 06:43 neverlandly 阅读(837) 评论(0) 推荐(0)

Leetcode: Guess Number Higher or Lower

摘要：Binary Search Here "My" means the number which is given for you to guess not the number you put into guess(int num). 阅读全文

posted @ 2016-11-28 05:33 neverlandly 阅读(401) 评论(0) 推荐(0)

Leetcode: Find K Pairs with Smallest Sums

摘要：Better Solution: O(KlogK), 转自https://discuss.leetcode.com/topic/50885/simple-java-o-klogk-solution-with-explanation Some observations: For every numbe 阅读全文

posted @ 2016-11-28 04:55 neverlandly 阅读(586) 评论(0) 推荐(0)

Leetcode: Super Pow

摘要：ab % k = (a%k)(b%k)%kSince the power here is an array, we'd better handle it digit by digit.One observation:a^1234567 % k = (a^1234560 % k) * (a^7 % k 阅读全文

posted @ 2016-11-28 01:48 neverlandly 阅读(398) 评论(0) 推荐(0)

Leetcode: Largest Divisible Subset

摘要：DP Solution similar to Longest Increasing Subsequence: 我的解法：用一个arraylist存以某一个element结尾的最长sequence 别人的好方法，大体思路一样，只是不存arraylist, 而用一个preIndex数组存以某一个elem 阅读全文

posted @ 2016-11-27 01:24 neverlandly 阅读(429) 评论(0) 推荐(0)

Leetcode: Water and Jug Problem && Summary: GCD求法（辗转相除法 or Euclidean algorithm）

摘要：参考：https://discuss.leetcode.com/topic/49238/math-solution-java-solution The basic idea is to use the property of Bézout's identity and check if z is a 阅读全文

posted @ 2016-11-27 00:10 neverlandly 阅读(655) 评论(0) 推荐(0)

Leetcode: Sum of Two Integers && Summary: Bit Manipulation

摘要：转自https://discuss.leetcode.com/topic/49771/java-simple-easy-understand-solution-with-explanation/2，注意里面对于减法的讲解 have been confused about bit manipulati 阅读全文

posted @ 2016-11-26 11:53 neverlandly 阅读(349) 评论(0) 推荐(0)

Leetcode: Max Sum of Rectangle No Larger Than K

摘要：Reference: https://discuss.leetcode.com/topic/48875/accepted-c-codes-with-explanation-and-references/2 The naive solution is brute-force, which is O(( 阅读全文

posted @ 2016-11-26 08:01 neverlandly 阅读(644) 评论(0) 推荐(0)

Leetcode: Count Numbers with Unique Digits

摘要：Analysis: A number of unique digits is a number which is a combination of unrepeated digits. So, we can calculate the total number. for number with n 阅读全文

posted @ 2016-11-26 04:20 neverlandly 阅读(340) 评论(0) 推荐(0)

Leetcode: Design Twitter

摘要：注意需要maintain一个time stamp, 每次postTweet时++。还有要注意unfollow的时候，不能unfollow自己关于PriorityQueue还看到这一种写法，挺简单的： 1 Set<Integer> users = userMap.get(userId).follow 阅读全文

posted @ 2016-11-26 01:58 neverlandly 阅读(435) 评论(0) 推荐(0)

Leetcode: Nth Digit

摘要：1-9 : count:9 * len:1 10-99： count:90 * len:2 100-999: count:900 * len:3 1000-9999: count: 9000 * len:4 maintain a count, len, start 阅读全文

posted @ 2016-11-25 06:51 neverlandly 阅读(303) 评论(0) 推荐(0)

Leetcode: Russian Doll Envelopes

摘要：DP 解法， Time Complexity: O(N^2) sort based on width or height, anyone is ok. After the sorting, for each envelope, those envelopes which can fit into t 阅读全文

posted @ 2016-11-25 05:36 neverlandly 阅读(594) 评论(0) 推荐(0)

Leetcode: Data Stream as Disjoint Intervals && Summary of TreeMap

摘要：TreeMap 解法： Use TreeMap to easily find the lower and higher keys, the key is the start of the interval.Merge the lower and higher intervals when neces 阅读全文

posted @ 2016-11-25 02:06 neverlandly 阅读(420) 评论(0) 推荐(0)

Leetcode: Valid Perfect Square

摘要：我的binary Search 解法：无需变成long 别人三种方法总结：阅读全文

posted @ 2016-11-24 12:50 neverlandly 阅读(330) 评论(0) 推荐(0)

Leetcode: Intersection of Two Arrays II

摘要：用HashMap Follow Up 1: 用two pointer解，可以省存成HashMap Follow Up 2: 用在长的数组里面binary Search可解 Follow Up 3: What if elements of nums2 are stored on disk, and t 阅读全文

posted @ 2016-11-24 11:52 neverlandly 阅读(285) 评论(0) 推荐(0)

Leetcode: Intersection of Two Arrays

摘要：Use two hash sets Time complexity: O(n) 注意Set<Integer> set = new HashSet<>(); 第二个泛型可以不写出 Iterator iter = set2.iterator(); for (int i=0; i<res.length; 阅读全文

posted @ 2016-11-24 10:34 neverlandly 阅读(319) 评论(0) 推荐(0)

Leetcode: Top K Frequent Elements

摘要：很像majority element III, 但是那道题有O(k) extra space的限制，这里没有。有任意extra space, 同时知道elem range情况下，bucket sort最节省时间语法上注意第5行，建立一个ArrayList的array，后面没有泛型generic L 阅读全文

posted @ 2016-11-24 06:51 neverlandly 阅读(315) 评论(0) 推荐(0)

Leetcode: Reverse Vowels of a String

摘要：Two Pointers 解法，注意大小写阅读全文

posted @ 2016-11-24 05:20 neverlandly 阅读(273) 评论(0) 推荐(0)

随笔分类 - Leetcode