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 { * […]
Permutation Sequence The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, We get the following sequence (ie, for n = 3): “123” “132” “213” “231” “312” “321” Given n and k, return the kth permutation sequence. Note: Given n […]
Spiral Matrix II Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example, Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ] […]
Length of Last Word Given a string s consists of upper/lower-case alphabets and empty space characters ‘ ‘, return the length of last word in the string. If the last word does not exist, return 0. Note: A word is defined as a character sequence consists of non-space characters only. […]
Insert Interval Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9]. Example 2: Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and […]
