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…

Number of 1 Bits Write a function that takes an unsigned integer and return the number of '1' bits it has (also known as the Hamming weight). Example 1: Input: 00000000000000000000000000001011 Output: 3 Explanation: The input binary string 0000000000…

今天先谈下弗洛伊德判环,弗洛伊德判环原来是在一个圈内有两人跑步,同时起跑,一人的速度是另一人的两倍,则那个人能在下一圈追上另一个人,弗洛伊德判环能解数字会循环出现的题,比如说判断一个链表是不是循环链表.在程序中具体表现为 one = change(one); //一倍速度 two = change(change(two));//两倍速度 即一倍速度的人调用生成函数change一次,两倍速度的人调用生成函数change两次. Leetcode 202 Happy Number 就是这样一道简单的题…

临近毕业了,对技术有种热爱的我也快步入码农行业了,以前虽然在学校的ACM学习过一些算法,什么大数的阶乘,dp,背包等,但是现在早就忘在脑袋后了,哈哈,原谅我是一枚菜鸡,为了锻炼编程能力还是去刷刷LeetCode吧       LeetCode收录了许多互联网公司的算法题目,被称为刷题神器.       主要的目的:       1.熟悉各互联网公司的算法题目,为找工作做准备,也为更好滴掌握编程能力.       2.复习以前学过的编程语言如java,c,c++,C#,LeetCode支持几乎所有…

Happy Number Write an algorithm to determine if a number n 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 pr…

Additive Number Additive number is a string whose digits can form additive sequence. A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the prec…

Ugly Number II Write a program to find the n-th ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. Example: Input: n = 10 Output: 12 Explanation: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugl…

Largest Number Given a list of non negative integers, arrange them such that they form the largest number. Example 1: Input: [10,2] Output: "210" Example 2: Input: [3,30,34,5,9] Output: "9534330" Note: The result may be very large, so…

Given an array of integers, every element appears three times except for one. Find that single one. Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 题解:线性时间,O(1)的空间复杂度,只能把整数写成二进制的形式运算了.具体…

Validate if a given string is numeric. Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => true 题解:题目不难,就是有点麻烦,要注意的地方很多,总结一下: 前面和后面的空格要用s.trim()去掉: 前导的'+'和'-'号需要忽略:…