约瑟夫问题

<?php

// Josephu Quession
class Person {
    public $no;
    public $next = NULL;

    public function __construct($no) {
        $this->no = $no;
    }
}

class RoundList {
    public $head = NULL;
    public $tail = NULL;

    public function __construct($n) {
        $this->create($n);
    }

    private function create($n) {
        for ($i = 1; $i <= $n; $i += 1) {
            if ($i == 1) {
                $this->head = $this->tail = new Person($i);
            } else {
                $this->tail->next = new Person($i);
                $this->tail = $this->tail->next;
            }
        }
        $this->tail->next = $this->head;
    }

    function delete($p) {
        $curr = $this->head;
        $flag = TRUE;
        while ($curr->next != $p) {
            $curr = $curr->next;
            if ($curr == $this->head) {
                $flag = FALSE;
                break;
            }
        }
        if ($flag) {
            // 删除节点是头节点
            if ($curr == $this->tail) {
                $this->head = $this->head->next;
                $curr->next = $this->head;
            }
            // 删除节点是尾节点
            else if ($curr->next == $this->tail) {
                $curr->next = $this->tail->next;
                $this->tail = $curr;
            }
            // 删除节点是中间节点
            else {
                $curr->next = $curr->next->next;
            }
        }
        // 返回删除节点的next节点
        return $curr->next;
    }
}


// $n个人围坐一圈，第$k个人开始计数，数到$m的人出列
function josephu($n, $k, $m) {
    $ret = array();
    $rl = new RoundList($n);
    for ($i = 0; $i < $k; $i += 1) {
        if ($i == 0) {
            $p = $rl->head;
        } else {
            $p = $p->next;
        }
    }

    for ($i = 0; $i < $n; $i += 1) {
        for ($j = 1; $j < $m; $j += 1) {
            $p = $p->next;
        }
        $ret[] = $p->no;
        $p = $rl->delete($p);
    }
    //return $ret;
    print '<pre>';
    print_r($ret);
    print '</pre>';
}

josephu(20, 5, 7);