臻舍

1.题目：包含重复（Contains Duplicate 2）  Given an array of integers and an integer k, find out whether there there are two distinct indices i and j in the array such that nums[i] = nums[j] and the d

1.题目：单链表的逆转（循环和递归）思路：循环：用两个指针p1,p2,p1指向node，p2指向node->next;在将p2->next指向p1前，先将p2->next保存下来。然后将p1,p2依次往后挪动递归：将链表拆分为表头节点和余下链表，将余下链表逆序后，再表头节点链接到逆序后的余下链表中注：对于线性数据结构，比较适合用迭代循环方法，而对于树状数据结构，比如二叉树，递归方法

1.题目Count Primes（计算质数个数）Count the number of prime numbers less than a non-negative number, n.计算小于n的非负数中质数的个数思路：对于每一个数k，检查是否能被2到sqrt(k)整除代码：class Solution {public: int countPrimes(int

1.题目：Invert Binary Tree/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), righ

1.Roman to Integer(将罗马数字转化为整数)   Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. 思路：1）罗马数字到整数的转换规则个位数举例I,1 】II,2】 III,3】 IV,4 】V,5