Remove Duplicates from Sorted List II Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. For example, Given 1->2->3->3->4->4->5, return 1->2->5. Given 1->1->1->2->3, return 2->3. 困倦时不要解题，这题做了3遍才AC。 一个bonus，删掉多余的node，以免内存溢出。 我用了superHead的技巧，不用再单独判断链表的起始情况。 查看当前节点和下一个节点，如果相同，将isDuplicated置1.当遇到当前节点和下一节点不同时，看isDuplicated的值，如果是1，则忽略掉它，把isDuplicated置0.如果是0，证明当前节点没有重复，连入结果链表中。 /** * Definition for singly-linked list. * struct ListNode { […]

Remove Duplicates from Sorted Array II 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 should return length = 5, and A is now [1,1,2,2,3]. 很奇怪的题，和此题的第一代没有本质区别。 只要增加一个变量count记录当前已经出现的相同数字的个数。 如果count>2，不移动start，如果小于等于2，copy A[i] to A[start++]。 class Solution { public: int […]

Search a 2D Matrix Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right. The first integer of each row is greater than the last integer of the previous […]

Set Matrix Zeroes Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. click to show follow up. Follow up:Did you use extra space? A straight forward solution using O(mn) space is probably a bad idea. A […]

Given an absolute path for a file (Unix-style), simplify it. For example, path = “/home/”, => “/home” path = “/a/./b/../../c/”, => “/c” click to show corner cases. Corner Cases: Did you consider the case where path = “/../”? In this case, you should return “/”. Another corner case is the […]

Text Justification Given an array of words and a length L, format the text such that each line has exactly L characters and is fully (left and right) justified. You should pack your words in a greedy approach; that is, pack as many words as you can in each line. […]

Add Binary Given two binary strings, return their sum (also a binary string). For example, a = “11” b = “1” Return “100”. 二进制加法，注意进位。和字符串访问时的末尾对齐。 class Solution { public: string addBinary(string a, string b) { if(a.empty()) return b; else if(b.empty()) return a; int carry = 0; string sum; int i = […]

Plus One Given a non-negative number represented as an array of digits, plus one to the number. The digits are stored such that the most significant digit is at the head of the list. Show Tags 注意进位，从vector末尾扫向开头。 class Solution { public: vector<int> plusOne(vector<int> &digits) { if(digits.size() == 0) return digits; […]

Valid Number Validate if a given string is numeric. Some examples: “0” => true ” 0.1 ” => true “abc” => false “1 a” => false “2e10” => true Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one. […]