Question

How to implement the collatz sequence in PHP

Answer 1

/*
 
- The sequence begins with a positive integer: n
- If n is odd, the next number is: 3n+1
- If n is even, the next number is: n/2
- The sequence ends with: 1
 
*/

function collatz_sequence($n) {
    echo $n . " ";
    while ($n > 1) {
        if ($n % 2 == 0) { // even
            $n = $n / 2;
        }
        else { // odd
            $n = 3 * $n + 1;
        }
        echo $n . " ";
    }
}


collatz_sequence(7);




/*
run:

7 22 11 34 17 52 26 13 40 20 10 5 16 8 4 2 1 

*/

 

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