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. […]

Unique Paths II Follow up for “Unique Paths”: Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the middle of […]

Unique Paths A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ […]

Rotate List Given a list, rotate the list to the right by k places, where k is non-negative. For example: Given 1->2->3->4->5->NULL and k = 2, return 4->5->1->2->3->NULL. 陷阱挺多，需要小心。 1. 如果链表为空或k==0，return head; 2. 如果k>链表长度count, k = k % count; /** * Definition for singly-linked list. * struct ListNode { * […]