Leetcode - 随笔分类(第30页) - neverlandly

Leetcode: Add Two Numbers

摘要：You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single ... 阅读全文

posted @ 2014-06-06 23:56 neverlandly 阅读(250) 评论(0) 推荐(0)

Leetcode: Word Ladder II

摘要：Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that:Only one letter can be ch... 阅读全文

posted @ 2014-06-05 21:07 neverlandly 阅读(393) 评论(0) 推荐(0)

Leetcode: Triangle

摘要：Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the fol... 阅读全文

posted @ 2014-05-29 23:57 neverlandly 阅读(274) 评论(0) 推荐(0)

Leetcode: Best Time to Buy and Sell Stock II

摘要：Say you have an array for which the ith element is the price of a given stock on day i.Design an algorithm to find the maximum profit. You may complet... 阅读全文

posted @ 2014-05-29 04:03 neverlandly 阅读(269) 评论(0) 推荐(0)

Leetcode: Best Time to Buy and Sell Stock

摘要：这道题求进行一次交易能得到的最大利润。如果用brute force的解法就是对每组交易都看一下利润，取其中最大的，总用有n*(n-1)/2个可能交易，所以复杂度是O(n^2)。跟Maximum Subarray非常类似，用“局部最优和全局最优解法”。思路是维护两个变量，一个是到目前为止最好的交易，另阅读全文

posted @ 2014-05-29 03:37 neverlandly 阅读(386) 评论(0) 推荐(0)

Leetcode: Pascal's Triangle II

摘要：Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].Note:Could you optimize your algorithm to use ... 阅读全文

posted @ 2014-05-28 05:44 neverlandly 阅读(414) 评论(0) 推荐(0)

Leetcode: Pascal's Triangle

摘要：Given numRows, generate the first numRows of Pascal's triangle.For example, given numRows = 5,Return[ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6... 阅读全文

posted @ 2014-05-28 04:29 neverlandly 阅读(235) 评论(0) 推荐(0)

Leetcode: Path Sum II

摘要：Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example: Given the below binary tree and su 阅读全文

posted @ 2014-05-23 06:14 neverlandly 阅读(460) 评论(0) 推荐(0)

Leetcode: Convert Sorted Array to Binary Search Tree

摘要：Given an array where elements are sorted in ascending order, convert it to a height balanced BST.基本上一次过，要注意边界条件的问题：如果在recursion里有两个参数int begin, end, 递... 阅读全文

posted @ 2014-05-23 03:39 neverlandly 阅读(299) 评论(0) 推荐(0)

Leetcode: Merge Sorted Array

摘要：Given two sorted integer arrays A and B, merge B into A as one sorted array.Note:You may assume that A has enough space (size that is greater or equal... 阅读全文

posted @ 2014-05-23 02:56 neverlandly 阅读(262) 评论(0) 推荐(0)

Leetcode: Word Search

摘要：Remember to change the character back after loop through all the possibility 非常聪明的方法1：O（1）空间的话可以不用visited数组，直接改board。改了之后，再访问的时候因为board[i][j] != word. 阅读全文

posted @ 2014-05-22 23:45 neverlandly 阅读(657) 评论(0) 推荐(0)

Leetcode: Remove Duplicates from Sorted Array II

摘要：Follow up for "Remove Duplicates": What if duplicates are allowed at most twice? For example, Given sorted array A = [1,1,1,2,2,3], Your function shou 阅读全文

posted @ 2014-05-21 12:33 neverlandly 阅读(246) 评论(0) 推荐(0)

Leetcode: Subsets

摘要：Adopted approach: Notice that in line 11, you should create a copy of current path, and add it to res. Otherwise, it'll be edited later, and be wiped 阅读全文

posted @ 2014-05-21 12:25 neverlandly 阅读(572) 评论(1) 推荐(0)

Leetcode: Combinations

摘要：Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.For example,If n = 4 and k = 2, a solution is:[ [2,4], [3,4... 阅读全文

posted @ 2014-05-21 05:54 neverlandly 阅读(327) 评论(0) 推荐(0)

Leetcode: Climbing Stairs

摘要：这道题目是求跑楼梯的可行解法数量。每一步可以爬一格或者两个楼梯，可以发现，递推式是f(n)=f(n-1)+f(n-2)，也就是等于前一格的可行数量加上前两格的可行数量。熟悉的朋友可能发现了，这个递归式正是斐波那契数列的定义. 这里base case 是f(1)=1, f(2)=2. Fibonacc 阅读全文

posted @ 2014-05-20 07:10 neverlandly 阅读(377) 评论(0) 推荐(0)

Leetcode: Set Matrix Zeroes

摘要：一次过，空间复杂度为O(m+n), 下一次做的时候寻找constant space solution。用boolean array也可以，用bit vector可能会更节省. 其实还可以再优化，我们考虑使用第一行和第一列来记录上面所说的行和列的置0情况，这里问题是那么第一行和第一列自己怎么办？想要记阅读全文

posted @ 2014-05-20 07:08 neverlandly 阅读(307) 评论(0) 推荐(0)

Leetcode: Search a 2D Matrix

摘要：1 Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: 2 3 Integers in each row are ... 阅读全文

posted @ 2014-05-20 06:56 neverlandly 阅读(358) 评论(0) 推荐(0)

Leetcode: Add Binary

摘要：Given two binary strings, return their sum (also a binary string).For example,a = "11"b = "1"Return "100".我自己的做法：用StringBuffer, a和b都从末尾扫描到开头，而StringBu... 阅读全文

posted @ 2014-05-14 11:26 neverlandly 阅读(238) 评论(0) 推荐(0)

Leetcode: Unique Paths

摘要：推荐方法：DP矩阵做法其实还可以节省一维：2D矩阵变成一维数组DP：一维DP方法2：阅读全文

posted @ 2014-05-14 06:01 neverlandly 阅读(373) 评论(0) 推荐(0)

Leetcode: Trapping Rain Water

摘要：这道题做的比较艰辛，一开始自己想的是一个用stack的解法，感觉过于繁琐（出栈，入栈，计算容积），但未尝不是一个好的尝试，这个方法还是有点小问题，过后会好好想清楚。看了网上提示完成了最终的方法，这个方法两次遍历数组，第一次遍历找每个元素右边最大的元素，第二次遍历寻找每个元素左边最大的元素，同时计算该阅读全文

posted @ 2014-05-14 04:37 neverlandly 阅读(601) 评论(0) 推荐(0)

随笔分类 - Leetcode