百草园

摘要： Given a binary tree, find the maximum path sum.The path may start and end at any node in the tree.For example:Given the below binary tree, 1 / \ 2 3Return6.后序遍历！ 1 /** 2 * Definition for binary tree 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode... 阅读全文

摘要： Given a singly linked listL:L0→L1→…→Ln-1→Ln,reorder it to:L0→Ln→L1→Ln-1→L2→Ln-2→…You must do this in-place without altering the nodes' values.For example,Given{1,2,3,4}, reorder it to{1,4,2,3}.OH! MY GOD! I HATE LINKED LIST!看似简单，实现起来总会遇到各种指针错误，写程序之前最好先在纸上好好画画，把各种指针关系搞搞清楚。本题的想法就是先将列表平分成两份，后一份逆序，然 阅读全文

摘要： Write an efficient algorithm that searches for a value in anmxnmatrix. This matrix has the following properties:Integers in each row are sorted from l... 阅读全文

摘要： Given a set of candidate numbers (C) and a target number (T), find all unique combinations inCwhere the candidate numbers sums toT.Thesamerepeated number may be chosen fromCunlimited number of times.Note:All numbers (including target) will be positive integers.Elements in a combination (a1,a2, … ,ak 阅读全文

摘要： There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).好难啊，总是会有各种边界问题。想法如下：最后从medianof two sorted arrays中看到了一种非常好的方法。原文用英文进行解释，在此我们将其翻译成汉语。该方法的核心是将原问题转变成一个寻找第k小数的问题（假设两个原序列升序排列），这样中位数实际上是第(m+n 阅读全文

摘要： 题目描述：又到毕业季，很多大公司来学校招聘，招聘会分散在不同时间段，小明想知道自己最多能完整的参加多少个招聘会(参加一个招聘会的时候不能中断或离开)。输入：第一行n，有n个招聘会，接下来n行每行两个整数表示起止时间，由从招聘会第一天0点开始的小时数表示。n 2 #include 3 #include 4 #include 5 using namespace std; 6 7 struct data { 8 int st; 9 int ed;10 };11 12 bool cmp(const data &a, const data &b) {13 return ... 阅读全文

摘要： Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.没啥好说的。 1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * ListNode *next; 6 * ListNode(int x) : val(x), next(... 阅读全文

摘要： Given two integersnandk, return all possible combinations ofknumbers out of 1 ...n.For example,Ifn= 4 andk= 2, a solution is:[ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4],]DFS！ 1 class Solution { 2 public: 3 void getNextComb(vector > &res, vector v, int n, int k, int idx) { 4 if (idx ... 阅读全文

摘要： Follow up for problem "Populating Next Right Pointers in Each Node".What if the given tree could be any binary tree? Would your previous solution stil... 阅读全文

摘要： Sort a linked list using insertion sort.虽然算法很简单，但是链表操作起来实正是烦啊，特别要注意各种边界条件。 1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * ListNode *next; 6 * ListNode(int x) : val(x), next(NULL) {} 7 * }; 8 */ 9 class Solution {10 public:11 ListNode *inser... 阅读全文