question

34. Search for a Range

Original Page

Given a sorted array of integers, find the starting and ending position of a given target value.

Your algorithm’s runtime complexity must be in the order of O(log n).

If the target is not found in the array, return [-1, -1].

For example,
Given [5, 7, 7, 8, 8, 10] and target value 8,
return [3, 4].

analysis

一开始就想到了二分查找，但是原来做二分查找的时候一般都是找到确定的那个数就完成了，
这里的情况比较特殊，需要找到整个区间，所以需要两遍查找，并且一个是找到小于target
的最大索引，一个是找到大于target的最大索引，代码参考leetcode discuss,这位仁
兄也做了详细的分析解释。

code

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class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        vector<int> ret(2, -1);
        int i = 0, j = nums.size() - 1;
        int mid;
        while(i < j){
            mid = (i + j) / 2;
            if(nums[mid] < target) i = mid + 1;
            else j = mid;
        }
        if(nums[i] != target) return ret;
        else {
            ret[0] = i;
            if((i+1) < (nums.size() - 1) && nums[i+1] > target){
                ret[1] = i;
                return ret;
            }
        }   //一点小优化
        j = nums.size() - 1;
        while(i < j){
            mid = (i + j) / 2 + 1;
            if(nums[mid] > target) j = mid - 1;
            else i = mid;
        }
        ret[1] = j;
        return ret;
    }
};

docker-mysql-cluster

基于docker搭了个mysql集群，稍微记一下，
首先是新建mysql主库容

玩一下swoole的websocket

WebSocket是HTML5开始提供的一种在单个TCP连接上进行全双工通讯的协议。WebSocket通信协议于2011年被IETF定为标准RFC 6455，WebSocketAPI被W3C定为标准。
,在web私信，im等应用较多。背景和优缺点可以参看wiki。

环境准备

因为swoole官方还不支持windows，所以需要装下linux,之前都是用ubuntu，
这次就试一下centos7，还是满好看的，虽然虚拟机会默认最小安装，需要在安装
时自己选择带gnome的，当然最小安装也是可以的，只是最后需要改下防火墙。
然后是装下PHP，Nginx什么的，我是用Oneinstack，可以按需安装
给做这个的大大点个赞。

Invert a binary tree

     4
   /   \
  2     7
 / \   / \
1   3 6   9

to

     4
   /   \
  7     2
 / \   / \
9   6 3   1

Trivia:
This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew),
but you can’t invert a binary tree on a whiteboard so fuck off.

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root == NULL) return root;
        TreeNode* temp;
        temp = invertTree(root->left);
        root->left = invertTree(root->right);
        root->right = temp;
        return root;
    }
};

*Longest Substring Without Repeating Characters *

problem

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input:(2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

分析（不用英文装逼了）
这个代码是抄来的，链接原作是这位大大。

Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

Reverse Bits

Reverse bits of a given 32 bits unsigned integer.

For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 00111001011110000010100101000000).

Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1’ bits it has (also known as the Hamming weight). For example, the 32-bit integer ‘11’ has binary representation 00000000000000000000000000001011, so the function should return 3.

Pcre

Perl Compatible Regular Expressions (PCRE) is a regular
expression C library inspired by the regular expression
capabilities in the Perl programming language, written
by Philip Hazel, starting in summer 1997.

因为最近工作内容的一部分需要做字符串的识别处理，所以就顺便用上了之前在PHP中用过的正则，在C/C++中本身不包含正则库，这里使用的pcre，对MFC开发，在这里提供了静态链接库，在引入lib跟.h文件后即可使用。