Month: December 2016

fibonacci

-base cases
fibonacci(0)=0
fibonacci(1)=1

-recursive case
fibonacci(n) = fibonacci(n-1)+fibonacci(n-2)
n > 1

A procedure, fibonacci, that takes a natural number as its input, and returns the value of that fibonacci number.

def fibonacci(n):
    if n == 0:
      return 0
    if n == 1:
      return n
    return fibonacci(n-1) + fibonacci(n-2)

fibonacci has interesting feature below
fibo(x) = fibo(x-n-1)

More faster fibonacci procedure using for loop.

def fibonacci(n):
    current = 0
    after = 1
    for i in range(0, n):
      current, after = after, current + after
    return current

mass_of_earth = 5.9722 * 10**24
mass_of_rabbit = 2

n = 1
while fibonacci(n) * mass_of_rabbit < mass_of_earth:
  n = n + 1
print n, fibonacci(n)

- Ranking web pages as popularity
popularity(p) = # of people who are friends with p
popularity(p) = Σ popularity(f), f E friends of p

def popularity(p):
score = 0
for f in friends(p):
score = score + popularity(f)
return score

Defining Procedures Recursively

factorial(n) = n*(n-1)*(n-2)*…1

factorial(n)=1
factorial(n)=n*factorial(n-1)

A procedure, factorial, that takes a natural number as its input, and returns the number of ways to arrange the input number of items.

def factorial(n):
 if n == 0:
   return 1
 else:
   return n * factorial(n-1)

Palindromes:match the first and last string, such as level.
A procedure is_palindrome, that takes as input a string, and returns a Boolean indicating if the input string is a palindrome.

def is_palindrome(s):
  if s == "":
    return True
  else:
    if s[1] == s[-1]:
        return is_palindrome(s[1:-1])
    else:
        return false

Another way, using for loop, to write palindrome procedure.

def iter_palindrome(s):
  for i in range(0, len(s)/2):
    if s[i] != s[-(i + 1)]:
      return False
  return True

vps

ログイン後に、言語設定

[root@tk2-234-26826 ~]# yum update
Loaded plugins: fastestmirror, security
Setting up Update Process
Loading mirror speeds from cached hostfile
 * base: ftp.iij.ad.jp
 * epel: ftp.riken.jp
 * extras: ftp.iij.ad.jp
 * updates: ftp.iij.ad.jp
No Packages marked for Update

[root@tk2-234-26826 ~]# vim /etc/sysconfig/i18n

userの設定

[root@tk2-234-26826 ~]# date
2016年 12月  5日 月曜日 12:39:36 JST
[root@tk2-234-26826 ~]# useradd user

権限の変更

[root@tk2-234-26826 ~]# usermod -G wheel user
[root@tk2-234-26826 ~]# visudo

sudo権限の変更

## Allows people in group wheel to run all commands
%wheel  ALL=(ALL)       ALL

ドキュメントルート　/www/root/html

Ajaxを使ってMySQLの更新をHTML側で自動更新

$(“”).empty();で、一旦データを空にして、setTimeout、countupで自動更新します。

<!DOCTYPE html>
<html lang="ja">
<head>
    <meta charset="utf-8">
    <title>Ajax</title>

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
    <script>
    // setTimeout関数で2秒ごとに取得
    var countup = function(){
    $("#content").empty();
    $(document).ready(function(){
      // /**
      // * Ajax通信メソッド
      // * @param type
      // * @param url
      // * @param dataType
      // ** /
      $.ajax({
      type: "POST",
      url: 'json.php',
      dataType: "json",

      success: function(data, dataType)
      {
        if(data == null) alert('データが0件でした');

        var $content = $('#content');
        for (var i = 0; i<data.length; i++)
        {
          $content.append("<li>" + data[i].name + "</li>");
        }
      },
      error: function(XMLHttpRequest, textStatus, errorThrown)
      {
        alert('Error : ' + errorThrown);
      }
    });
  });
    setTimeout(countup, 2000);
  }
  countup();
    </script>
  </head>
  <body>
    <h1>sample</h1>
    <ul id="content"></ul>
  </body>
</html>

ページ閲覧中のオンラインユーザ表示方法

session_id()で、mysqlにセッションIDと時間を保存していき、mysql_num_rowsでセッション数が保存されている行をカウントし、一定時間経過したらセッションIDを削除します。

<?php
session_start();
$session=session_id();
$time=time();
$time_check=$time-300;

$host="localhost";
$username="dbuser";
$password="xxxx";
$db_name="online";
$tbl_name="online_user";

mysql_connect("$host", "$username", "$password") or die("could not connect to server.");
mysql_select_db("$db_name") or die("cannot select DB");

$sql="SELECT * FROM $tbl_name WHERE session='$session'";
$result=mysql_query($sql);
$count=mysql_num_rows($result);

// if count is 0, then enter the values
if($count=="0"){
  $sql1="INSERT INTO $tbl_name(session, time)VALUES('$session', '$time')";
  $result1=mysql_query($sql1);
  }
  // else update the values
  else {
    $sql2="UPDATE $tbl_name SET time='$time' WHERE session='$session'";
    $result2=mysql_query($sql2);
  }

  $sql3="SELECT * FROM $tbl_name";
  $result3=mysql_query($sql3);
  $count_user_online=mysql_num_rows($result3);
  echo "<b>Users Online: </b> $count_user_online ";

  //after 5 minutes, session will be deleted
  $sql4="DELETE FROM $tbl_name WHERE time<$time_check";
  $result4=mysql_query($sql4);

  mysql_close();

?>

preg_match

郵便番号:/^[0-9]{3}-[0-9]{4}$/
電話番後：/^[0-9]{2,4}-[0-9]{2,4}-[0-9]{3,4}$/
E-mailアドレス:|^[0-9a-z_./?-]+@([0-9a-z-]+\.)+[0-9a-z-]+$|

filter_var(), FILTER_VALIDATE_EMAIL

The filter_var() function filters a variable with the specified filter.
Returns the filtered data on success, or FALSE on failure.
The FILTER_VALIDATE_EMAIL filter validates an e-mail address.

<?php
$email = "john.doe@example.com";

if (!filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
  echo("$email is a valid email address");
} else {
  echo("$email is not a valid email address");
}
?>