好玩的线上检测代码工具-codewars(1)

检测环境:
http://www.codewars.com
基本描述:

Task:

Your task is to write a function which returns the sum of following series upto nth term(parameter).

Series: 1 + 1/4 + 1/7 + 1/10 + 1/13 + 1/16 +…

Rules:

You need to round the answer to 2 decimal places and return it as String.
If the given value is 0 then it should return 0.00
You will only be given Natural Numbers as arguments.

Examples:

SeriesSum(1) => 1 = “1.00”
SeriesSum(2) => 1 + 1/4 = “1.25”
SeriesSum(5) => 1 + 1/4 + 1/7 + 1/10 + 1/13 = “1.57”
NOTE: In PHP the function is called series_sum().

function series_sum($n) {
  // Your code here
  if($n == 0)
  {
    return '0.00';
  }

  $res = 0;
  $n = floor($n);
  if($n == 1)
  {
      return '1.00';
  }
  else
  {
    for($i = 1;$i <= 3*$n-2; $i = $i+3)
    {
       $res += 1/$i;
    }

    return (String) round($res, 2);
  }
}

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