A computer science problem by Spock Weakhypercharge

Computer Science Level 3 
//What value will this print out, rounded to the nearest hundredths?
void main ()
{
 int x=1;
 float kittens=0;
 while (x<600000000000)
 {
  if (x%2==1)
  {
   kittens=kittens+(1.0/(2*x-1));
  }
  else 
  {
   kittens=kittens-(1.0/(2*x-1));
  }
  x++;
 }
  kittens=4*kittens;
    printf("%f\n",kittens);
}


The answer is 3.14.

Spock Weakhypercharge by Spock Weakhypercharge , 96, USA

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4 solutions

Saumitra Paira
Mar 8, 2014

x is increasing by 1 each time, correspondingly values of kittens are operated as=1-1/3+1/5-1/7+--------------------=tan(inverse)(1)=pi/4 now kittens=4*pi/4; therefore kittens=pi=3.143--- thanks

5 Helpful 0 Interesting 0 Brilliant 0 Confused

I pretty much built this around that one formula: http://mathworld.wolfram.com/PiFormulas.html

Frankly there are tonnes of these identities and they are worth glancing over. It's funny how simple rules run complex things.

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Sanjay Kamath
Apr 6, 2014

No need to run the problem for the full number of iterations. Here an approximation does just fine.

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Sandeep Thakur
Mar 17, 2014

I ran this in JS, but with smaller number.. I got result 3.141605... I changed numbers, but got same result.. So thought that It will be same for that number as well.

Nearest hundredth is: 3.14 therefore...

0 Helpful 0 Interesting 0 Brilliant 0 Confused

JS is very nice, no? I feel like the only person who doesn't like Python very much, the lack of semicolons make it feel naked and the functions and loops aren't like any other language I know. This problem was published on Pi Day.

Spock Weakhypercharge - 7 years, 1 month ago

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