Check where number 1 is in decimal number

问题

I am having hundreds of numbers like:

I need to check where the number 1 is in those number, so basicly

1.00000000 = 1
0.10000000 = 2
0.01000000 = 3

I tried Round() function, but it sometimes prints numbers like 1.E-6 or something like that, I need exact location of number 1.

Thank you very much for help.

回答1:

I wouldn't rely too much on the approach you posted in your answer. Use the following function instead:

function index_of_one($dec)
{
  // maximum precision is 15
  $str = str_replace('.','',sprintf('%.15f', $dec));

  $pos = strpos($str, '1');

  if ($pos === false) {
    return -1;
  }

  return ($pos + 1);
}

Example:

$dec1 = 1.00000000;
$dec2 = 0.10000000;
$dec3 = 0.00010000;

echo index_of_one($dec1); // 1
echo index_of_one($dec2); // 2
echo index_of_one($dec3); // 5

Visit this link to test it.

回答2:

Looks like I found a solution, used strpos() function which works perfectly!

Basicly:

strpos(0.01000000, 1)

回答3:

I say using regex is suitable when micro-optimization is not top-priority, when it lessens total function calls, and when it provides a direct, desired result.

Considering your case and the sample input, preg_match_all('/[^.](?=[^1]*1)|1.*/',$number) does everything in one step. It matches each individual non-dot character that is later followed by a 1 OR from 1 to the end of the string.

(Regex Pattern Demo)

preg_match_all()'s return value is the number of matches, so it delivers exactly what you are asking for -- a count.

Effectively, dots are not counted nor are any of the characters after the first 1. If there is no 1 found, the count is 0 (not -1 as suggested by the other answer).

Here is a demonstration with a battery of tests (Demo):

$numbers=['0.00100000','0.10000000','0.01000000','1.00000000','0.00001000','0.00000100','0.00000000'];

foreach($numbers as $number){
    echo "$number = ",preg_match_all('/[^.](?=[^1]*1)|1.*/',$number),"\n";
}

Output:

0.00100000 = 4
0.10000000 = 2
0.01000000 = 3
1.00000000 = 1
0.00001000 = 6
0.00000100 = 7
0.00000000 = 0

来源：https://stackoverflow.com/questions/48054972/check-where-number-1-is-in-decimal-number

标签

php

regex

count

rounding