I am writting my own calculator on PHP.
I have a problem with my code because i don't know where i am trying to read too far in the string. So if anyone can enlighten me ..
The exact error i get is :
PHP Notice: Uninitialized string offset: 4 in /home/salim/Bureau/web/piscine_php/d01/ex11/do_op_2.php on line 76
Here is the code below :
function decoupe ($argv)
{
global $nbr1;
global $nbr2;
global $sign;
$string = NULL;
$string = trim($argv[1], " \t");
echo $string;
echo "\n";
$x = 0;
while($string[$x])
{
if (is_numeric($string[0]) == false)
error_msg();
if (is_numeric($string[$x]) && $string[$x + 1])
{
while (is_numeric($string[$x]))
{
$nbr1 .= $string[$x];
$x++;
}
}
if (is_thisoperator(substr($string, $x)))
{
$sign .= $string[$x];
$x++;
}
else
{
error_msg();
}
if ($string[$x + 1] && is_numeric($string[$x]))
{
while (is_numeric($string[$x]))
{
$nbr2 .= $string[$x];
$x++;
}
}
else
{
error_msg();
}
}
Don't use $string[$x] as a way to test whether $x is a valid index in the string. It prints a warning when $x is outside the string. Use $x < strlen($string) instead. So change:
while ($string[$x])
to
while ($x < strlen($string))
and change
if ($string[$x + 1] && is_numeric($string[$x]))
to
if ($x + 1 < strlen($string) && is_numeric($string[$x]))
I had a job interview test and the question I got was about making a function which would return the number of ways a number could be generated by using numbers from a certain set and any number in the set can be used N times.
It is like if I have the number 10 and I want to find out how many ways 10 can be generated using [2,3,5]
2+2+2+2+2 = 10
5+3+2 = 10
2+2+3+3 = 10
5+5 = 10
to solve it I made this function:
function getNumberOfWays($money, $coins) {
static $level = 0;
if (!$level) {
sort($coins);
}
if ($level && !$money) {
return 1;
} elseif (!$level && !$money) {
return 0;
}
if ($money === 1 && array_search(1, $coins) !== false) {
return 1;
} elseif ($money === 1 && array_search(1, $coins) === false) {
return 0;
}
$r = 0;
$tmpCoins = $coins;
foreach ($coins as $index => $coin) {
if (!$coin || $coin > $money) {
continue;
}
$tmpCoins[$index] = 0;
$tmpMoney = $money;
do {
$tmpMoney -= $coin;
if ($tmpMoney >= 0) {
$level++;
$r += getNumberOfWays($tmpMoney, $tmpCoins);
$level--;
} elseif (!$tmpMoney) {
$r++;
}
} while ($tmpMoney >= 0);
}
return $r;
}
This function works ok and returns the right value.
My question is if there is a better way for it.
Thanks
I have this PHP code which is supposed to increase a URL shortener mask on each new entry.
My problem is that it dosen't append a new char when it hits the last one (z).
(I know incrementing is a safety issue since you can guess earlier entries, but this is not a problem in this instance)
If i add 00, it can figure out 01 and so on... but is there a simple fix to why it won't do it on its own?
(The param is the last entry)
<?php
class shortener
{
public function ShortURL($str = null)
{
if (!is_null($str))
{
for($i = (strlen($str) - 1);$i >= 0;$i--)
{
if($str[$i] != 'Z')
{
$str[$i] = $this->_increase($str[$i]);
#var_dump($str[$i]);
break;
}
else
{
$str[$i] = '0';
if($i == 0)
{
$str = '0'.$str;
}
}
}
return $str;
}
else {
return '0';
}
}
private function _increase($letter)
{
//Lowercase: 97 - 122
//Uppercase: 65 - 90
// 0 - 9 : 48 - 57
$ord = ord($letter);
if($ord == 122)
{
$ord = 65;
}
elseif ($ord == 57)
{
$ord = 97;
}
else
{
$ord++;
}
return chr($ord);
}
}
?>
Effectively, all you are doing is encoding a number into Base62. So if we take the string, decode it into base 10, increment it, and reencode it into Base62, it will be much easier to know what we are doing, and the length of the string will take care of itself.
class shortener
{
public function ShortURL($str = null)
{
if ($str==null) return 0;
$int_val = $this->toBase10($str);
$int_val++;
return $this->toBase62($int_val);
}
public function toBase62($num, $b=62) {
$base='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$r = $num % $b ;
$res = $base[$r];
$q = floor($num/$b);
while ($q) {
$r = $q % $b;
$q =floor($q/$b);
$res = $base[$r].$res;
}
return $res;
}
function toBase10( $num, $b=62) {
$base='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$limit = strlen($num);
$res=strpos($base,$num[0]);
for($i=1;$i<$limit;$i++) {
$res = $b * $res + strpos($base,$num[$i]);
}
return $res;
}
}
how can I check for numbers only from -10 negative to +10 positive?
This is what I have, but I think it's not safe:
if(isset($_POST['number']) && ctype_digit($_POST['number']) && $_POST['number']>=-10 && $_POST['number']<=10){
//do something
}
and the form:
Input a number between -10 and 10: <input type="text" name="number" size="5" />
if( isset($_POST['number'])) {
$num = intval($_POST['number']);
if( $num >= -10 && $num <= 10) {
// do something
}
}
There are other ways, but that one will work. Anything that can't be converted to a number will be treated as zero. If this is not desired behaviour, add:
&& "".$num == $_POST['number']
To that inner IF statement, to ensure that no non-numeric characters were removed from the input.
Check whether a variable is a number including zero and negative values
$x = '-22';
if (isNumber($x, ['zero','negative']))
echo 'Yes';
else
echo 'No';
isNumber($x, $includes=[])
{
if (is_int($x)) {
if ($x === 0) {
if (in_array('zero', $includes))
return true;
} elseif ($x < 0) {
if (in_array('negative', $includes))
return true;
} else
return true;
} elseif (is_string($x)) {
if ($x == '0') {
if (in_array('zero', $includes))
return true;
} elseif ($x[0] == '-') {
if (in_array('negative', $includes))
return ctype_digit(substr($x, 1));
} else
return ctype_digit($x);
}
}
I have a large number of strings to process in php. I want to "fix" them to be title case (using ucwords(strtolower($str))) but only if they are all upper or all lower case already. If they are already mixed case, I'd just rather just leave them as they are.
What is the fastest way to check for this? It seems like foring through the string would be a rather slow way to go about it.
Here's what I have, which I think will be too slow:
function fixCase($str)
{
$uc = 0;
$lc = 0;
for($i=0;$i<strlen($str);$i++)
{
if ($str[$i] >= 'a' && $str[$i] <= 'z')
$lc++;
else if ($str[$i] >= 'A' && $str[$i] <= 'Z')
$uc++;
}
if ($uc == 0 || $lc == 0)
{
return ucwords(strtolower($str));
}
}
just use a string compare (case sensitive)
function fixCase($str)
{
if (
(strcmp($str, strtolower($str)) === 0) ||
(strcmp($str, strtoupper($str)) === 0) )
{
$str = ucwords(strtolower($str));
}
return $str;
}
There's not going to be any amazing optimization, because by the nature of the problem you need to look at every character.
Personally, I would just loop over the characters of the string with this sort of algorithm:
Look at the first character in the string, set a variable indicating whether it was upper or lowercase.
Now examine each character sequentially. If you get to the end of the string and they've all been the same case as the first character, fix the string's case as you like.
If any character is a different case than the first character was, break the loop and return the string.
Edit: actual code, I think this is about as good as you're going to get.
// returns 0 if non-alphabetic char, 1 if uppercase, 2 if lowercase
function getCharType($char)
{
if ($char >= 'A' && $char <= 'Z')
{
return 1;
}
else if ($char >= 'a' && $char <= 'z')
{
return 2;
}
else
{
return 0;
}
}
function fixCase($str)
{
for ($i = 0; $i < strlen($str); $i++)
{
$charType = getCharType($str[$i]);
if ($charType != 0)
{
$firstCharType = $charType;
break;
}
}
for ($i = $i + 1; $i < strlen($str); $i++)
{
$charType = getCharType($str[$i]);
if ($charType != $firstCharType && $charType != 0)
{
return $str;
}
}
if ($firstCharType == 1) // uppercase, need to convert to lower first
{
return ucwords(strtolower($str));
}
else if ($firstCharType == 2) // lowercase, can just ucwords() it
{
return ucwords($str);
}
else // there were no letters at all in the string, just return it
{
return $str;
}
}
You could try the string case test function I posted here
function getStringCase($subject)
{
if (!empty($subject))
{
if (preg_match('/^[^A-Za-z]+$/', $subject))
return 0; // no alphabetic characters
else if (preg_match('/^[^A-Z]+$/', $subject))
return 1; // lowercase
else if (preg_match('/^[^a-z]+$/', $subject))
return 2; // uppercase
else
return 3; // mixed-case
}
else
{
return 0; // empty
}
}
If the reason you want to avoid fixing already mixed-case strings is for efficiency then you are likely wasting your time, convert every string no matter its current condition:
function fixCase($str)
{
return ucwords(strtolower($str));
}
I would be very surprised if it ran any slower than the accepted answer for strings the length of those you would generally want to title case, and it's one less condition you need to worry about.
If, however, there is good reason to avoid converting already mixed-case strings, for example you want to preserve some intended meaning in the casing, then yes, jcinacio's answer is certainly the simplest and very efficient.
Wouldn't it be easier to check if the string = lowercase(string) or string = uppercase(string) and if so then leave it. Otherwise perform your operation.
Well I decided to do a test of the 2 proposed answers thus far and my original solution. I wouldn't have thought the results would turn out this way, but I guess native methods are /that/ much faster over all.
Code:
function method1($str)
{
if (strcmp($str, strtolower($str)) == 0)
{
return ucwords($str);
}
else if (strcmp($str, strtoupper($str)) == 0)
{
return ucwords(strtolower($str));
}
else
{
return $str;
}
}
// returns 0 if non-alphabetic char, 1 if uppercase, 2 if lowercase
function getCharType($char)
{
if ($char >= 'A' && $char <= 'Z')
{
return 1;
}
else if ($char >= 'a' && $char <= 'z')
{
return 2;
}
else
{
return 0;
}
}
function method2($str)
{
for ($i = 0; $i < strlen($str); $i++)
{
$charType = getCharType($str[$i]);
if ($charType != 0)
{
$firstCharType = $charType;
break;
}
}
for ($i = $i + 1; $i < strlen($str); $i++)
{
$charType = getCharType($str[$i]);
if ($charType != $firstCharType && $charType != 0)
{
return $str;
}
}
if ($firstCharType == 1) // uppercase, need to convert to lower first
{
return ucwords(strtolower($str));
}
else if ($firstCharType == 2) // lowercase, can just ucwords() it
{
return ucwords($str);
}
else // there were no letters at all in the string, just return it
{
return $str;
}
}
function method0($str)
{
$uc = 0;
$lc = 0;
for($i=0;$i<strlen($str);$i++)
{
if ($str[$i] >= 'a' && $str[$i] <= 'z')
$lc++;
else if ($str[$i] >= 'A' && $str[$i] <= 'Z')
$uc++;
}
if ($uc == 0 || $lc == 0)
{
return ucwords(strtolower($str));
}
}
function test($func,$s)
{
$start = gettimeofday(true);
for($i = 0; $i < 1000000; $i++)
{
$s4 = $func($s);
}
$end = gettimeofday(true);
echo "$func Time: " . ($end-$start) . " - Avg: ".sprintf("%.09f",(($end-$start)/1000000))."\n";
}
$s1 = "first String";
$s2 = "second string";
$s3 = "THIRD STRING";
test("method0",$s1);
test("method0",$s2);
test("method0",$s3);
test("method1",$s1);
test("method1",$s2);
test("method1",$s3);
test("method2",$s1);
test("method2",$s2);
test("method2",$s3);
Results:
method0 Time: 19.2899270058 - Avg: 0.000019290
method0 Time: 20.8679389954 - Avg: 0.000020868
method0 Time: 24.8917310238 - Avg: 0.00002489
method1 Time: 3.07466816902 - Avg: 0.000003075
method1 Time: 2.52559089661 - Avg: 0.000002526
method1 Time: 4.06261897087 - Avg: 0.000004063
method2 Time: 19.2718701363 - Avg: 0.000019272
method2 Time: 35.2485661507 - Avg: 0.000035249
method2 Time: 29.3357679844 - Avg: 0.000029336
Note that anything that looks only at [A-Z] will be incorrect as soon as there are accented or umlaut characters. Optimizing for speed is meaningless if the result is incorrect (hey, if the result doesn't have to be correct, it can write you a REALLY fast implementation...)