Renzhouzhou的博客

问题：https://leetcode.com/problems/power-of-two/?tab=Description Given an integer, write a function to determine if it is a power of two. 给定一个数，判断它是不是2的幂数。 分析：二进制来说，2的幂数都是首位是1，其他位是0。所以用n&(n-1)是否为0可以判断

问题：https://leetcode.com/problems/sqrtx/ Implement int sqrt(int x).Compute and return the square root of x. 计算x的平方根。 分析：二分法计算。不是整数的取整数部分。 C++代码：class Solution {public: int mySqrt(int x) {

问题：https://leetcode.com/problems/add-digits/?tab=Description Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. 给定一个非负的整数，求它各位和，直到出现最终个位数，返回这个个位数。也就是

问题：https://leetcode.com/problems/excel-sheet-column-title/?tab=Description Given a positive integer, return its corresponding column title as appear in an Excel sheet. For example: 1 -> A 2

问题：https://leetcode.com/problems/excel-sheet-column-number/?tab=Description Related to question Excel Sheet Column Title。 Given a column title as appear in an Excel sheet, return its corresponding co

问题：https://leetcode.com/problems/factorial-trailing-zeroes/?tab=Description Given an integer n, return the number of trailing zeroes in n!. 给定一个整数n，返回n!的末尾0的个数，要求对数阶时间复杂度。 分析：产生0是因为2*5才有，而n!中2的个数永远比

问题：https://leetcode.com/problems/reverse-integer/?tab=Description Reverse digits of an integer.Example1: x = 123, return 321 Example2: x = -123, return -321 给定一个整数，求它逆序后的数。如果逆序后的数越界了，返回0. 分析：用y

问题：https://leetcode.com/problems/missing-number/?tab=Description Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array. 给一个有序的序列，找出缺少的数。

问题：https://leetcode.com/problems/power-of-three/?tab=Description Given an integer, write a function to determine if it is a power of three. 给定一个整数，判断它是不是3的幂数。 分析：不能用递归和循环。任何一个3的i次方一定能被最大的3的i次方整除。 C

问题：https://leetcode.com/problems/valid-perfect-square/?tab=Description Given a positive integer num, write a function which returns True if num is a perfect square else False. 给定一个正数，如果它是某一个数的平方则返回tr

问题：https://leetcode.com/problems/nth-digit/?tab=Description Find the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, **分析：**S1=1 S2=12 S3=123 S4=1234 … S9=123456789

问题：https://leetcode.com/problems/add-strings/?tab=Description Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.给定两个字符串形式的正整数num1和num2，计算num1和num2之和。

问题：https://leetcode.com/problems/roman-to-integer/?tab=Description Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. 给一个罗马数字，把它转为整数。输入的数是1到39

问题：https://leetcode.com/problems/arranging-coins/?tab=Description You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins.Given n, find t

问题：https://leetcode.com/problems/palindrome-number/?tab=Description Determine whether an integer is a palindrome. Do this without extra space. 判断一个整数是否是回文数。不能增加额外的空间。 分析： 因为不能增加额外的空间，所以每次比较头的数和末尾的数

问题： https://leetcode.com/problems/minimum-moves-to-equal-array-elements/?tab=Description Given a non-empty integer array of size n, find the minimum number of moves required to make all array element

问题：https://leetcode.com/problems/ugly-number/?tab=Description 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,

问题：https://leetcode.com/problems/add-binary/?tab=Description Given two binary strings, return their sum (also a binary string). For example,a = “11”b = “1” Return “100”. 给两个二进制数，返回它们的和，仍然用二进制表示。