echo viralAdvertising(5)."\n\n";
echo viralAdvertising(10);

function viralAdvertising($n) {
	$liked = 2;
	$shared = 0;
	$cumulative = 2;

for ($i = 2; $i <= $n; $i++) {
		$shared = $liked*3;
		$liked = floor($shared/2);
		$cumulative += $liked;
	}
	return $cumulative;
}

plusMinus([-3, -5, 6, 7, 0, 0, 2, 4, -5, 3]);
//plusMinus([2 ,1,0, 0, 0, -6 ,-4, 10, 3, -7])."\n\n";
//plusMinus([1, 2, -6, -3, 8, 0 , 0, 1,-9, 4])."\n\n";


//calculate a ratio of positive, negative and 0 numbers in array
function plusMinus($arr){
	$r=[0,0,0];
	
	foreach ($arr as $item){
		if ($item>0){
			$r[0]++;
		}else if ($item<0){
			$r[1]++;
		}else{
			$r[2]++;
		}
	}
	//number of items in entire array
	$s = count($arr);
    // Calculates each ratio and rounds the result to 6 digits
    $res = [round($r[0]/$s, 6), round($r[1]/$s, 6), round($r[2]/$s, 6)];
    
    echo $res[0] . "\n";
    echo $res[1] . "\n";
    echo $res[2] . "\n";
	
}

echo repeatedString("mango", 10);

function repeatedString($string, $number) {
	$ltr = 'a'; //letter function
	$strl = strlen($string);

	$res = substr_count($string, $ltr)*floor($number/$strl);

	$res += substr_count(substr($string, 0, $number%$strl), $ltr);

}
return $res;

print_r(stones(4, 10, 100));

// Compute all possible numbers that might occur on the last stone
function stones($n, $a, $b) {
    
    $res = [];
    
    $n_z_s = $n - 1;
    
    // If the difference between $a and $b is 0, 
    // there will be only one possible answer
    if ($a == $b) {
        return [$n_z_s * $a];
    }
    
    // Needs to choose min and max of the numbers 
    // to loop through the possible answers
    $min = min($a, $b);
    $max = max($a, $b);
    
    // As the pattern shows (from the Explanation) the difference  
    // of the answer's numbers is exactly the same as the difference  
    // between the last two parameters: $a and $b, in this case: 90
    $diff = $max - $min;
    for ($i = $n_z_s*$min;  $i <= $max*$n_z_s;  $i += $diff) {
        $res[] = $i;
    }
    return $res;
}


/*
With differences 10 and 100, all possible series are the following:
0, 10, 20, 30
0, 10, 20, 120
0, 10, 110, 120
0, 100, 110, 120
0, 10, 110, 210
0, 100, 110, 210
0, 100, 200, 210
0, 100, 200, 300
Hence the answer 30 120 210 300
As the pattern shows (from the Explanation) the difference  
of the answer's numbers is exactly the same as the difference  
between the last two parameters: $a and $b, in this case: 90
*/

echo libraryFine_3(10, 7, 2015, 7, 7, 2015)."\n\n";
echo libraryFine_3(10, 8, 2015, 5, 3, 2015)."\n\n";
echo libraryFine_3(10, 7, 2017, 5, 7, 2015)."\n\n";
echo libraryFine_3(10, 7, 2017, 10, 7, 2017)."\n\n";

//Using if and else if functions
function libraryFine($d1, $m1, $y1, $d2, $m2, $y2) {
	$hacks = 0; //fine unit hackos
	$a = $d1-$d2;
	$b = $m1-$m2;
	$c = $y1-$y2;

	if ($a == 0 && $b == 0 && $c == 0) {
		$hacks = 0;
	} else {
		if ($a != 0) {
			$hacks = 15*$a;
		}if ($b != 0) {
			$hacks = 500*$b;
		}if ($c != 0) {
			$hacks = 10000;
		}
		return $hacks;
	}
}  //This is my idea, maybe good, maybe not so


//Using switch function
function libraryFine_2($d1, $m1, $y1, $d2, $m2, $y2) {
	$hacks = 0;
	$a = $d1-$d2;
	$b = $m1-$m2;
	$c = $y1-$y2;

	switch ($hacks) {
		case ($a == 0 && $b == 0 && $c == 0):
			$hacks = 0;
			break;
		case ($a != 0):
			$hacks = 15*$a;
			break;
		case ($b != 0):
			$hacks = 500*$b;
			break;
		case ($c != 0):
			$hacks = 10000;
			break;
	}
	return $hacks;
}  // doesn't work

// Calculates the fine, if the book is returned late
function libraryFine_3($d1, $m1, $y1, $d2, $m2, $y2) {
    
    $hacks = 0;
    
    // If the book is returned after the calendar 
    // year, there is a fixed fine of 10,000 Hackos
    if ($y1 > $y2) {
        $hacks = 10000;
    } 
    
    // If the book is returned after the expected return 
    // month but still within the same calendar year
    else if ($m1 > $m2  &&  $y1 == $y2) {
        $hacks = 500 * ($m1 - $m2);
    }
    
    // If the book is returned after the expected return 
    // day but still within the same calendar month and year
    else if ($d1 > $d2  &&  $m1 == $m2  &&  $y1 == $y2) {
        $hacks = 15 * ($d1 - $d2);
    }
    return $hacks;
} //fastets solution

<?php
echo convertKilometersToMiles(56)."\n";
echo convertMilesToKilometers(265.56)."\n";

function convertKilometersToMiles($km){
$mile = 0.621371;
return $km * $mile;
}

function convertMilesToKilometers($miles){
$one_miles = 0.621371;
return $miles * $one_miles;
}

echo "6 - ".checkNumber(6)."\n\n";
echo "9 - ".checkNumber(9)."\n\n";
echo "12 - ".checkNumber(12)."\n\n";

function checkNumber($num) {
	$res = 'Deficient';

	if ($num == 1) {
		return false;
	}

	$sqrt = sqrt($num);

	$sum = 1;
	// Loops starting 2 to the square root of the given number
	for ($i = 2; $i <= $sqrt; $i++) {
		if ($num%$i == 0) {
			$sum += $i;

			$result = $num/$i;
			// If $i is not equal to the square root,
			// then adds it to the $sum variable
			if ($result != $i) {
				$sum += $result;
			}
		}
	}
	if ($sum == $num) {
		$res = 'Perfect';
	} else if ($sum > $num) {
		$res = 'Abundant';
	}
	return $res;
}

print_r(findPrimeNumbers(50));

//Prime numbers are evenly divided by themselves and by one
//Finds first N prime number
function findPrimeNumbers($n){
	$num=2;//first  prime number is 2
	$res=[];
	while  (0<$n){
		$cnt=0;
		for ($i=2; $i<=$num; $i++){
			if ($num%$i==0){
				$cnt++;
			}
		}
		if ($cnt==1){
			$res[]=$num;
			$n--;
		}
		$num++;
	}
	return $res;
}

echo century(1756)."\n";
echo century(1555)."\n";
echo century(1000)."\n";
echo century(1001)."\n";
echo century(2005)."\n";


// Get the Century
function century($year) {
	$suf = 'th';
	if ($year > 2000) {
		$suf = 'st';
	}
	return ceil($year/100).$suf.' century';
}