Codility - PtrListLen 알고리즘 풀이


회사에서 면접 진행하기 앞 서, 면접자에게 문제를 주기 전

먼저 Codility 문제를 풀어보고 난이도를 판단해서 문제를 고르기로하여 간단하게 문제를 풀어보았다.

A pointer is called a linked list if:

  • it is an empty pointer (it is then called a terminator or an empty list); or
  • it points to a structure (called a node or the head) that contains a value and a linked list (called the tail).
  • The length of a list is defined as the total number of nodes it contains. In particular, an empty list has length 0.

For example, consider the following linked list:

A -> B -> C -> D ->

This list contains four nodes: A, B, C and D. Node D is the last node and its tail is the terminator. The length of this list is 4.

Assume that the following declarations are given:

class IntList {  var $value = 0;  var $next = NULL;}

Write a function:

function solution($L);

that, given a non-empty linked list L consisting of N nodes, returns its length.

For example, given list L shown in the example above, the function should return 4.

Assume that:

N is an integer within the range [1..5,000];

list L does not have a cycle (each non-empty pointer points to a different structure).

In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.

작성한 코드

function solution($m)


     // var_dump($m);

     $counter = 0;

     while ( $m ) {

         $m = $m->next;



    //   var_dump($counter);

     return $counter;


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