Leetcode - 随笔分类(第14页) - neverlandly

Leetcode: Longest Substring with At Least K Repeating Characters

摘要：Analysis: Given a string s, find out all chars that are invalid (i.e., count < k). The longest substring must reside in one of the substrings divided 阅读全文

posted @ 2016-12-01 11:33 neverlandly 阅读(426) 评论(0) 推荐(0)

Leetcode: Rotate Function

摘要：F(0) = (0 * 4) + (1 * 3) + (2 * 2) + (3 * 6) = 0 + 3 + 4 + 18 = 25 [4, 3, 2, 6] F(1) = (0 * 6) + (1 * 4) + (2 * 3) + (3 * 2) = 0 + 4 + 6 + 6 = 16 [6, 阅读全文

posted @ 2016-12-01 08:12 neverlandly 阅读(224) 评论(0) 推荐(0)

Leetcode: UTF-8 Validation

摘要：这道题题干给出了判断 one single UTF-8 char的方法，然后给一个UTF-8 char sequence，判断是不是正确sequence. (读题读了很久) 这道题关键是要学到用 & 取出一个bit sequence当中几位的方法二进制数表示法：在前面加 0b, 八进制加0o, 十阅读全文

posted @ 2016-12-01 07:09 neverlandly 阅读(732) 评论(0) 推荐(0)

Leetcode: Decode String

摘要：自己的做法：这种括号问题肯定是用栈，最好是先在栈里存一个空元素，然后stack.peek().append()各种操作一个栈存string, 一个栈存number，维护一个指针numStart指向数字的开始 1. 遇到数字啥也不做 2. 遇到char： stack.peek().append(c 阅读全文

posted @ 2016-12-01 05:07 neverlandly 阅读(472) 评论(0) 推荐(0)

Leetcode: Perfect Rectangle

摘要：Refer to https://discuss.leetcode.com/topic/56052/really-easy-understanding-solution-o-n-java and https://discuss.leetcode.com/topic/55923/o-n-solutio 阅读全文

posted @ 2016-12-01 02:12 neverlandly 阅读(557) 评论(0) 推荐(0)

Leetcode: Random Pick Index

摘要：Three types of answer: Map Solution, O(N) memory, O(N) init, O(1) pick. Like @dettier's Reservoir Sampling. O(1) init, O(1) memory, but O(N) to pick. 阅读全文

posted @ 2016-11-30 12:23 neverlandly 阅读(407) 评论(0) 推荐(0)

Leetcode: Sum of Left Leaves

摘要：Recursion: 是不是left子数完全由bottom往上第二层决定，如果是left子树且是叶子节点，那么就是left leaves, parent得告诉child是不是在left子树 BFS: 阅读全文

posted @ 2016-11-30 11:45 neverlandly 阅读(365) 评论(0) 推荐(0)

Leetcode: Is Subsequence

摘要：Basic Solution: DP, O(mn) time, O(m) space, m is the size of s, n is the size of t Greedy Solution: O(n) time, O(1) space Follow Up: The best solution 阅读全文

posted @ 2016-11-30 11:09 neverlandly 阅读(1184) 评论(0) 推荐(0)

Leetcode: Elimination Game

摘要：refer to https://discuss.leetcode.com/topic/59293/java-easiest-solution-o-logn-with-explanation Time Complexity: O(log n) update and record head in ea 阅读全文

posted @ 2016-11-30 06:52 neverlandly 阅读(356) 评论(0) 推荐(0)

Leetcode: Find the Difference

摘要：O（N）time, O(1) space 阅读全文

posted @ 2016-11-30 05:40 neverlandly 阅读(247) 评论(0) 推荐(0)

Leetcode: Longest Absolute File Path

摘要：Time Complexity: O(N) The depth of the directory/file is calculated by counting how many "\t"s are there.The time complexity is O(n) because each subs 阅读全文

posted @ 2016-11-30 05:19 neverlandly 阅读(360) 评论(0) 推荐(0)

Leetcode: Mini Parser

摘要：有括号这种一般要用stack, stack top 就是当前着眼的那一个NestedInteger, 可以对其添加新的元素。注意47行判断很关键，顺带处理了 "[]," 括号后面是逗号的情况阅读全文

posted @ 2016-11-30 02:28 neverlandly 阅读(374) 评论(0) 推荐(0)

Leetcode: First Unique Character in a String

摘要：Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: s = "leetcode" return 0. s = "loveleetcode", return 2. Note: You may a... 阅读全文

posted @ 2016-11-29 12:24 neverlandly 阅读(306) 评论(0) 推荐(0)

Leetcode: Lexicographical Numbers

摘要：Solution 1: Solution 2: O(N) time, O(1) space The basic idea is to find the next number to add.Take 45 for example: if the current number is 45, the n 阅读全文

posted @ 2016-11-29 11:59 neverlandly 阅读(332) 评论(0) 推荐(0)

Leetcode: Shuffle an Array

摘要：Random random = new Random(); random.nextInt(int i); 阅读全文

posted @ 2016-11-29 10:53 neverlandly 阅读(560) 评论(0) 推荐(0)

Leetcode: Ransom Note

摘要：using one array 阅读全文

posted @ 2016-11-29 06:41 neverlandly 阅读(297) 评论(0) 推荐(0)

Leetcode: Linked List Random Node

摘要：Solution 1: Reservior sampling: (wiki introduction) Reservoir sampling is a family of randomized algorithms for randomly choosing a sample of k items 阅读全文

posted @ 2016-11-29 06:19 neverlandly 阅读(513) 评论(0) 推荐(0)

Leetcode: Insert Delete GetRandom O(1) - Duplicates allowed

摘要：The idea is to add a set to the hashMap to remember all the locations of a duplicated number. 阅读全文

posted @ 2016-11-29 02:44 neverlandly 阅读(525) 评论(0) 推荐(0)

Leetcode: Insert Delete GetRandom O(1)

摘要：最先想到是用double LinkedList+Map, 没必要，arraylist+map就够了；另外取random的方法还有，rand.nextInt(int n) returns an integer in the range [0, n) java.util.Random rand = ne 阅读全文

posted @ 2016-11-29 01:27 neverlandly 阅读(533) 评论(0) 推荐(0)

Leetcode: Kth Smallest Element in a Sorted Matrix

摘要：Heap: you need to know the row number and column number of that element(so we can create a tuple class here) Binary Search方法：（12/28仔细看了之后觉得没必要深究，有时间再去阅读全文

posted @ 2016-11-28 13:02 neverlandly 阅读(426) 评论(0) 推荐(0)

随笔分类 - Leetcode