Created
April 27, 2017 22:40
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Code snippet with math lession
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<?php | |
/** | |
* Code snippet with math lession | |
* @author Nguyen Nhu Tuan <tuanquynh0508@gmail.com> | |
*/ | |
// 2^3 = 8 | |
echo getExponential(2, 3); | |
echo '<br/>'; | |
// 2 + 2^2 + 2^3 | |
// = 2 + 4 + 8 | |
// = 14 | |
echo sumOfExponential(2, 3); | |
echo '<br/>'; | |
// false | |
$str1 = 'abcba'; | |
if (isSymmetryString($str1)) { | |
echo "'$str1' is symmetry <br/>"; | |
} else { | |
echo "'$str1' is not symmetry <br/>"; | |
} | |
// true | |
$str2 = 'abccba'; | |
if (isSymmetryString($str2)) { | |
echo "'$str2' is symmetry <br/>"; | |
} else { | |
echo "'$str2' is not symmetry <br/>"; | |
} | |
#------------------------------------------------------------------------------- | |
/** | |
* Get Exponential | |
* Calculate Exponential expression | |
* Example: x^n like pow(x, n) function of php | |
* @author Nguyen Nhu Tuan <tuanquynh0508@gmail.com> | |
* | |
* @param integer $a | |
* @param integer $n | |
* @return integer | |
*/ | |
function getExponential($a, $n) | |
{ | |
if ($n === 1) { | |
return $a; | |
} | |
return $a * getExponential($a, $n-1); | |
} | |
/** | |
* Sum Of Exponential | |
* Calculate Sum Of Exponential expression | |
* Example: x + x^2 + x^3 + ... + x^n | |
* @author Nguyen Nhu Tuan <tuanquynh0508@gmail.com> | |
* | |
* @param integer $a | |
* @param integer $n | |
* @return integer | |
*/ | |
function sumOfExponential($a, $n) | |
{ | |
if ($n === 1) { | |
return $a; | |
} | |
return pow($a, $n) + sumOfExponential($a, $n-1); | |
} | |
/** | |
* Is Symmetry String | |
* Check string is symmetry or not | |
* Example: abcba is not symmetry, but abccba is symmetry | |
* @author Nguyen Nhu Tuan <tuanquynh0508@gmail.com> | |
* | |
* @param string $str | |
* @return boolean | |
*/ | |
function isSymmetryString($str) | |
{ | |
if (strlen($str) % 2 != 0) { | |
return false; | |
} | |
for ($i=0; $i < strlen($str)/2; $i++) { | |
if (substr($str, $i, 1) != substr($str, -($i+1), 1)) { | |
return false; | |
} | |
} | |
return true; | |
} |
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