Leetcode - 随笔分类(第23页) - neverlandly

摘要：这道题就是BT的Level Order Traversal，每次要换一层的时候，记录当前节点注意，每次都是先添加右边child，所以是i==0的时候add 阅读全文

posted @ 2015-04-11 07:06 neverlandly 阅读(789) 评论(0) 推荐(0)

摘要：DFS的Flood Fill方法，不使用额外visited数组，但是用‘1’变成‘2’表示visited的方法复杂度时间 O(NM) 空间 O(max(N,M)) 递归栈空间 Union Find: (Quick Union) follow up是找最大岛的面积，想法是设置两个全局变量 max 阅读全文

posted @ 2015-04-11 05:20 neverlandly 阅读(2351) 评论(0) 推荐(0)

Leetcode: Reverse Bits

摘要：Reverse Integer那道题会考虑溢出，因为那是reverse each digit，这里不会溢出，因为reverse的是each bit Q：如果该方法被大量调用，或者用于处理超大数据（Bulk data）时有什么优化方法？A：这其实才是这道题的精髓，考察的大规模数据时算法最基本的优化方法阅读全文

posted @ 2015-03-14 07:06 neverlandly 阅读(775) 评论(0) 推荐(0)

Leetcode: Number of 1 Bits

摘要：Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).For example, the 32-bit i... 阅读全文

posted @ 2015-03-14 06:02 neverlandly 阅读(478) 评论(0) 推荐(0)

Leetcode: Best Time to Buy and Sell Stock IV

摘要：这道题在Best Time to Buy and Sell Stock III做过，那道题只是把k取了2而已递推式依然是 local[i][j]=max(global[i-1][j-1]+max(diff,0),local[i-1][j]+diff)， global[i][j]=max(local 阅读全文

posted @ 2015-03-01 12:40 neverlandly 阅读(3460) 评论(0) 推荐(0)

Leetcode: Reverse Words in a String II

摘要：这道题要求in-place做法，不能使用extra space, 那么，做法跟Rotate Array那道题非常相似（1）reverse the whole array （2）reverse each subarray seperated by ' ' 注意不要忘了reverse最后一个word 阅读全文

posted @ 2015-03-01 07:49 neverlandly 阅读(6591) 评论(0) 推荐(0)

Leetcode: Repeated DNA Sequence

摘要：Naive 方法就是两层循环，外层for(int i=0; i<=s.length()-10; i++), 内层for(int j=i+1; j<=s.length()-10; j++), 比较两个字符串s.substring(i, i+10)和s.substring(j, j+10)是否equal 阅读全文

posted @ 2015-03-01 07:31 neverlandly 阅读(477) 评论(1) 推荐(0)

Leetcode: Rotate Array

摘要：Rotate an array of n elements to the right by k steps.For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].Note:... 阅读全文

posted @ 2015-03-01 05:19 neverlandly 阅读(1722) 评论(0) 推荐(0)

Leetcode: Largest Number

摘要：聪明方法：其实干嘛要挨个比呢，按最直接的方法，接起来，谁大谁在前：可以换一下思路，要想比较两个数在最终结果中的先后位置，何不直接比较一下不同组合的结果大小？举个例子：要比较3和34的先后位置，可以比较334和343的大小，而343比334大，所以34应当在前。这样，有了比较两个数的方法，就可以阅读全文

posted @ 2015-01-29 07:31 neverlandly 阅读(479) 评论(0) 推荐(1)

Leetcode: Dungeon Game

摘要：The demons had captured the princess (P) and imprisoned her in the bottom-right corner of a dungeon. The dungeon consists of M x N rooms laid out in a... 阅读全文

posted @ 2015-01-29 00:07 neverlandly 阅读(717) 评论(0) 推荐(0)

Leetcode: Binary Search Tree Iterator

摘要：Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.Calling next() will return the ne... 阅读全文

posted @ 2015-01-28 07:36 neverlandly 阅读(534) 评论(0) 推荐(0)

Leetcode: Two Sum III - Data structure design

摘要：The trade off should be considered: In fact, there has to be one operation's time complexity is O(n) and the other is O(1), no matter add or find. So 阅读全文

posted @ 2015-01-27 12:51 neverlandly 阅读(3524) 评论(0) 推荐(0)

Leetcode: Two Sum II

摘要：Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.The function ... 阅读全文

posted @ 2015-01-27 12:02 neverlandly 阅读(400) 评论(0) 推荐(0)

Leetcode: Fraction to Recurring Decimal

摘要：Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.If the fractional part is repeating,... 阅读全文

posted @ 2015-01-27 09:10 neverlandly 阅读(391) 评论(0) 推荐(0)

Leetcode: Compare Version Numbers

摘要：这道题的意思用一个例子说明就是1.2 < 1.10, 因为1.10跟1.1是不一样的，1.10代表tenth revision. 而1.1代表first revision。所以这道题要按“.”分段，然后分段比较，方法是用split函数把string 分段，每一段挨个比过去。这里参考了网上的一个小技巧阅读全文

posted @ 2015-01-27 05:09 neverlandly 阅读(461) 评论(0) 推荐(0)

Leetcode: Maximum Gap

摘要：Given an unsorted array, find the maximum difference between the successive elements in its sorted form.Try to solve it in linear time/space.Return 0 ... 阅读全文

posted @ 2015-01-26 12:49 neverlandly 阅读(330) 评论(0) 推荐(0)

Leetcode: Missing Ranges

摘要：第二遍做法：参考下面一个vimukthi的解答 https://discuss.leetcode.com/topic/18612/accepted-java-solution-with-explanation/3 low 表示next possible missing integer streak的阅读全文

posted @ 2015-01-26 10:31 neverlandly 阅读(793) 评论(0) 推荐(0)

Leetcode: One Edit Distance

摘要：注意这道题：Must be exactly one distance apart. Not the same. 另外FB面经有一道比较狠的这个题的变形：这题就是one edit distance的变形题，难点在于给的Iterator，事先不知道两个file的长度，也不允许用extra space（阅读全文

posted @ 2015-01-24 05:46 neverlandly 阅读(1285) 评论(0) 推荐(0)

Leetcode: Longest Substring with At Most Two Distinct Characters

摘要：方法一：用HashMap, map里面存元素及其出现次数。维护一个最大长度。用两个指针，右指针一直走到出现3个dinstinct character为止。然后调整左指针删元素，直接从左往右逐个字符的删除，一直删到某个字符不会再出现。判断字符被删光就看次数是否减为了0. 采用方法：这里每个元素都会进阅读全文

posted @ 2015-01-22 13:17 neverlandly 阅读(400) 评论(0) 推荐(0)

Leetcode: Read N Characters Given Read4 II - Call multiple times

摘要：这道题跟I不一样在于，read函数可能多次调用，比如read(buf,23)之后又read(buf, 25), 第一次调用时的buffer还没用完，还剩一个char在buffer里，第二次拿出来接着用，这样才能保证接着上次读的地方继续往下读。 1. 所以应该设置这4个char的buffer为inst 阅读全文

posted @ 2015-01-22 07:35 neverlandly 阅读(2821) 评论(0) 推荐(0)

随笔分类 - Leetcode