Integer to Roman Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. 逐区间做处理. 解法一:非递归 class Solution { public: string intToRoman(int num) { string ret; //M<-->1000 ) { ret += 'M'; num -= ; } //t…

作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 个人公众号:负雪明烛 本文关键词:roman, 罗马数字,题解,leetcode, 力扣,Python, C++, Java 目录 题目描述 题目大意 解题方法 日期 题目描述 Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X…

题目: Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. 思路: 主要是了解罗马数和阿拉伯数字的对应关系,如下表: 由这个表基本上可以将1-3999范围的阿拉伯数字换成罗马数字.在处理阿拉伯数字时从高位开始匹配,将每个位的值找出对应罗马数字,串成字符串即可. public class Solution { public String…

题目描述: Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. 解题思路: 注意到用例比较少,所以采用以空间换时间的方法,把所有的结果列出,然后组合出输入值n的字符串即可. 具体代码: public class Solution { public static String intToRoman(int num) { String[]…

一天一道LeetCode系列 (一)题目 Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. (二)解题 将整形数字转换成罗马数字 罗马数字共有七个,即I(1),V(5),X(10),L(50),C(100),D(500),M(1000) 举例:Ⅰ.Ⅱ.Ⅲ.Ⅳ.Ⅴ.Ⅵ.Ⅶ.Ⅷ.Ⅸ.Ⅹ.Ⅺ.Ⅻ表示1-11 代码: class Solut…

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. 题解: 观察 1 到 10 :Ⅰ,Ⅱ,Ⅲ,Ⅳ(IIII),Ⅴ,Ⅵ,Ⅶ,Ⅷ,Ⅸ,Ⅹ,Ⅺ 难点在于出现字符不能连续超过三次,以及大数左边至多有一个小数.所以要分情况:1 - 3,4,5 - 8,9.将小数在大数左边的情况摘出来. Solution 1 贪心策略 class Solutio…

[LeetCode]397. Integer Replacement 解题报告(Python) 标签: LeetCode 题目地址:https://leetcode.com/problems/integer-replacement/description/ 题目描述: Given a positive integer n and you can do operations as follow: If n is even, replace n with n/2. If n is odd, you…

12 - Integer to Roman Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. Solution: 枚举,考虑每个字符以及每两个字符的组合 1 class Solution { 2 public: 3 string intToRoman(int num) { //runtime:28ms 4 string ret; 5…

我现在在做一个叫<leetbook>的免费开源书项目,力求提供最易懂的中文思路,目前把解题思路都同步更新到gitbook上了,需要的同学可以去看看 书的地址:https://hk029.gitbooks.io/leetbook/ 012. Integer to Roman[M] 问题 Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 数学解法 动态规划 日期 题目地址:https://leetcode.com/problems/integer-break/description/ 题目描述 Given a positive integer n, break it into the sum of at least two positive integers and maximize…

这道题是LeetCode里的第7道题. 题目描述: 给出一个 32 位的有符号整数,你需要将这个整数中每位上的数字进行反转. 示例 1: 输入: 123 输出: 321  示例 2: 输入: -123 输出: -321 示例 3: 输入: 120 输出: 21 注意: 假设我们的环境只能存储得下 32 位的有符号整数,则其数值范围为 [−231,  231 − 1].请根据这个假设,如果反转后整数溢出那么就返回 0. 首先,这是一道简单题,根据我多年的做题经验来看,这道题肯定有坑,绝对会有 IN…

Reverse digits of an integer. Example1: x = 123, return 321Example2: x = -123, return -321 总结:处理整数溢出的方法 ①用数据类型转换long  或 long long ②在每次循环时先保存下数字变化之前的值,处理后单步恢复看是否相等 (比③好) ③整体恢复,看数字是否相等. 思路:注意30000这样以0结尾的数字,注意越界时返回0. 我检查越界是通过把翻转的数字再翻转回去,看是否相等. int rever…

题目描述: Reverse digits of an integer. Example1: x = 123, return 321Example2: x = -123, return -321 很简单的题目其实用个数组就能解决了,不过用了一下queue,注意负数的情况. class Solution { public: int reverse(int x) { bool flg=false; ){ flg=true; x=-x; } queue<int> a; ){ a.push(x%); x…

Integer to English Words Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1. For example, 123 -> "One Hundred Twenty Three" 12345 -> "Twelve Thousand Three Hundred For…

题目大意:给定数字,将其转化为罗马数字的形式 罗马数字其实只有 I V X L C D M 这几种形式,其余均为组合的,去百度了解一下就ok. 所以首先想到的就是,将个.十.百.千位的数字构造出来,然后直接用就好了. 要特别注意为整10,整100.1000的情况. String [] ge ={"I","II","III","IV","V","VI","VII",&q…

1. 原题链接 https://leetcode.com/problems/integer-to-roman/description/ 2. 题目要求 (1) 将整数转换成罗马数字: (2) 整数的范围1-3999 3. 关于罗马数字 (1)对应整数 罗马数字 I V X L C D M 对应整数 1 5 10 50 100 500 1000 (2)罗马数字的书写规则 相同的数字连写, 所表示的数等于这些数字相加得到的数.如 XXX表示 30 小的数字在大的数字的右边, 所表示的数等于这些数字相…

12. 整数转罗马数字 知识点:字符串 题目描述 罗马数字包含以下七种字符: I, V, X, L,C,D 和 M. 字符 数值 I 1 V 5 X 10 L 50 C 100 D 500 M 1000 例如, 罗马数字 2 写做 II ,即为两个并列的 1.12 写做 XII ,即为 X + II . 27 写做  XXVII, 即为 XX + V + II . 通常情况下,罗马数字中小的数字在大的数字的右边.但也存在特例,例如 4 不写做 IIII,而是 IV.数字 1 在数字 5 的左边,…

First Missing Positive Given an unsorted integer array, find the first missing positive integer. For example,Given [1,2,0] return 3,and [3,4,-1,1] return 2. Your algorithm should run in O(n) time and uses constant space. 解法一:O(nlogn) time and O(1) sp…

Merge Sorted Array Given two sorted integer arrays A and B, merge B into A as one sorted array. Note: You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initializ…

Palindrome Linked List Given a singly linked list, determine if it is a palindrome. Follow up:Could you do it in O(n) time and O(1) space? 解法一: 一次遍历,装入vector,然后再一次遍历判断回文. 时间复杂度O(n),空间复杂度O(n) /** * Definition for singly-linked list. * struct ListNode…

Reverse Linked List Reverse a singly linked list. click to show more hints. Hint: A linked list can be reversed either iteratively or recursively. Could you implement both? 解法一:非递归 /** * Definition for singly-linked list. * struct ListNode { * int va…

Number of Islands Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are…

Combination Sum II Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. Each number in C may only be used once in the combination. Note: All numbers (including t…

Longest Valid Parentheses Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length…

Pow(x, n) Implement pow(x, n). 按照定义做的O(n)肯定是TLE的. 利用这个信息:x2n = (xn)2 有个注意点,当n为负是,直接取反是不可行的. 由于int的表示范围是[2-31, 231-1],当n为INT_MIN时,取反会溢出. 因此需要对n==INT_MIN单独考虑. 另外,除以2可以用右移1位来实现. 解法一:递归 class Solution { public: double pow(double x, int n) { ) { if(n == I…

Single Number II Given an array of integers, every element appears threetimes except for one. Find that single one. Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 解法一:开辟map记录次数 class So…

Longest Common Prefix Write a function to find the longest common prefix string amongst an array of strings. 解法一: 思路:设置一个位数记录器num,遍历所有字符串的第num位.如果都相同,则num++. 直到某字符串结束或者所有字符串的第num位不都相同,则返回[0~num-1]位,即最长公共前缀. class Solution { public: string longestComm…

Search Insert Position Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. You may assume no duplicates in the array. Here are few examples.[1,3,5,…

Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 解法一: 使用unordered_map记录当前节点是否被访问过,如访问过说明有环,如到达尾部说明无环. /** * Definition for singly-linked list. * struct ListNode { * int va…

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 simple…