Difference between revisions of "Interview Questions"

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==PHP==
 
==PHP==
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===abstract class===
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[[PHP interview]]
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Can not be Instantiable.(cannot become instant. Can only be inherited)<br>
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<pre>
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abstract class Fruit {
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private $color;
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abstract public function eat()
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public function setColor($c) {
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  $this->color = $c;
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}
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}
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</pre>
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<b>Difference between Abstract Class and Interface</b><br>
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Abstract Classes<br>
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An abstract class can provide some functionality and leave the rest for derived class<br>
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The derived class may or may not override the concrete functions defined in base class<br>
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The child class extended from an abstract class should logically be related<br><br>
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Interface<br>
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An interface cannot contain any functionality. It only contains definitions of the methods<br>
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The derived class must provide code for all the methods defined in the interface<br>
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Completely different and non-related classes can be logically be grouped together using an interface<br>
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===Single or Double Quotes?===
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<pre>
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//Sometimes people use double quotes in PHP to avoid having to use the period to separate code. For example, you could write:
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$color='red';
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echo "I have a $color shirt on today<br/>";
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//Faster however is not always better. A better way to write this code would be:
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echo 'I have a ' .$color. ' shirt on today<br/>';
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echo 'I have a $color shirt on today<br/>';
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</pre>
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Output:
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<pre>
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I have a red shirt on today
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I have a red shirt on today
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I have a $color shirt on today
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</pre>
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===Avoid Mysql Injection===
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<pre class="php">
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$_POST['username'] = 'aidan';
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$_POST['password'] = "' OR ''='";
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$query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
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$passwd=mysql_real_escape_string($_POST['password']);
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$passwd1=addslashes($_POST['password']);
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echo $passwd."<br />";
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echo $passwd1."<br />";
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echo ($query);
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</pre>
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Output
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<pre>
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\' OR \'\'=\'
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\' OR \'\'=\'
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SELECT * FROM users WHERE user='aidan' AND password='' OR ''=''
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</pre>
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This would allow anyone to log in without a valid password.
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===Static method===
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Declaring class properties or methods as static makes them accessible without needing an instantiation of the class.
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<pre>
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<?php
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class Foo
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{
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    public static $my_static = 'foo';
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    public function staticValue() {
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        return self::$my_static;
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    }
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}
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class Bar extends Foo
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{
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    public function fooStatic() {
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        return parent::$my_static;
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    }
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}
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print Foo::$my_static . "\n";
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$foo = new Foo();
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print $foo->staticValue() . "\n";
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print $foo->my_static . "\n";      // Undefined "Property" my_static
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print $foo::$my_static . "\n";
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$classname = 'Foo';
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print $classname::$my_static . "\n"; // As of PHP 5.3.0
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print Bar::$my_static . "\n";
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$bar = new Bar();
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print $bar->fooStatic() . "\n";
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</pre>
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==Swap 2 numbers in one line==
 
==Swap 2 numbers in one line==

Revision as of 23:08, 3 April 2012

Some Translation

n! Multiplicative

Object-oriented programming

Check here Interview_Questions(OOP)

C++ Interview

C++ interview

Javascript/Jquery

AJAX&Jquery

Algorithm Interview Problems

Algorithm Problems
All about Binary search tree
All about Linked List
Heap & Heap Sort

Regular Expression

http://www.zytrax.com/tech/web/regex.htm

PHP

PHP interview

Swap 2 numbers in one line

//swap
$a=10;
$b=20;
$a=$a+$b-($b=$a);
echo $a." and ". $b."\n";
// output 20 and 10
$a^=$b^=$a^=$b; //This has a bug. You cannot do things like this $a^=$a^=$a^=$a
echo $a." and ". $b;
//output 10 and 20

Calculate degree between hour and minute hand

<?php
$time=array();
$time['h']=12;
$time['m']=15;
$time['s']=30;
function clockDegree($time){
	$mPercent=((float)$time['m']+((float)$time['s']/60.0))/60.0;
	$mDegree=$mPercent*360;
	$hdegree=((int)$time['h']%12+(float)$mPercent)/12.0*360;
	echo abs($mDegree-$hdegree);
}
clockDegree($time);
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