目录 题目链接 注意点 解法 小结 题目链接 Letter Combinations of a Phone Number - LeetCode 注意点 可以不用按字典序排序 解法 解法一:输入的数字逐个处理,在已经生成的字符串后面追加该当前数字对应的所有字符.时间复杂度为O(n) class Solution { public: vector<string> letterCombinations(string digits) { vector<string> ans,temp_an…

目录 题目链接 注意点 解法 小结 题目链接 Palindrome Number - LeetCode 注意点 负数肯定是要return false的 数字的位数要分奇数和偶数两种情况 解法 解法一:将数字转化为字符串,然后对字符串从中间开始往两边拓展比较,要分长度为奇数和偶数的情况.时间复杂度为O(n) class Solution { public: bool isPalindrome(int x) { if(x<0 || (x%10 == 0 && x!=0)) { retur…

examination questions Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat…

Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the…

题目: Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is given below. Input:Digit string "23" Output: ["ad", "ae"…

Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330. Note: The result may be very large, so you need to return a string instead of an i…

Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is given below. Input:Digit string "23" Output: ["ad", "ae", &q…

问题描述: Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7. Note that 1…

问题描述: Given an array of integers, every element appears twice except for one. Find that single one. Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 要求:采用线性时间复杂度,并且最好不使用多余的空间. 一.位操作 异或运算,…

题目: Determine whether an integer is a palindrome. Do this without extra space. click to show spoilers. Some hints: Could negative integers be palindromes? (ie, -1) If you are thinking of converting the integer to string, note the restriction of using…