单链表练习题

1.单链表归并

/**
 * 有序的两个单链表归并
 * @param object $listA 待归并的单链表A
 * @param object $listB 待归并的单链表B
 * @return object $merge 归并之后的单链表
 */
function mergeLinkList($listA, $listB) {
    $p_a = $listA->head->next; // A的工作指针
    $p_b = $listB->head->next; // B的工作指针
    $merge = new LinkList(); // 存放结果的链表
    $m = $merge->head;
    while ($p_a && $p_b) {
        if ($p_a->data < $p_b->data) {
            $m->next = $p_a; // 指针传递
            $p_a = $p_a->next;
            $m = $m->next;
        } else {
            $m->next = $p_b;
            $p_b = $p_b->next;
            $m = $m->next;
        }            
    }
    while ($p_a) {
        $m->next = $p_a; // 指针传递
        $p_a = $p_a->next;    
        $m = $m->next;        
    }
    while ($p_b) {            
        $m->next = $p_b; // 指针传递
        $p_b = $p_b->next;        
        $m = $m->next;    
    }
    return $merge;
}

2.多项式加减运算

/*
 * @param object $polynomeA 用单链表存储的多项式A 数据格式是['index'=>指数, 'ratio'=>系数]
 * @param object $polynomeB 用单链表存储的多项式B 数据格式是['index'=>指数, 'ratio'=>系数]
 * @return object $polynomeC 计算之后的单链表
 */
function mergePolynome($polynomeA, $polynomeB) {
    if(!is_object($polynomeA) || !is_object($polynomeB)) return false;
    $polynomeC = new LinkList();
    $p_a =  $polynomeA->head->next;
    $p_b =  $polynomeB->head->next;
    $p_c =  $polynomeC->head;
    // 归并
    while ($p_a && $p_b) {
        if ($p_a->data['index'] < $p_b->data['index']) {
            $p_c->next = $p_a;
            $p_a = $p_a->next;
            $p_c = $p_c->next;
        } else if($p_a->data['index'] == $p_b->data['index']) {                
            if($p_a->data['ratio'] + $p_b->data['ratio'] != 0) {                     
                 $new_ration = $p_a->data['ratio'] + $p_b->data['ratio'];
                 $new_data = [];
                 $new_data['index'] = $p_a->data['index'];
                 $new_data['ratio'] = $new_ration;
                 $new = new node($new_data);
                 $p_c->next = $new;
                 $p_c = $new; // 是当前的，不是下一个的
            } 
            $p_a = $p_a->next;
            $p_b = $p_b->next;                                      
        } else {
            $p_c->next = $p_b;
            $p_b = $p_b->next;
            $p_c = $p_c->next;        
        }
    }
    while ($p_a) {
        $p_c->next = $p_a;
        $p_a = $p_a->next;
    }
    while ($p_b) {
        $p_c->next = $p_b;
        $p_b = $p_b->next;
    }
    return $polynomeC;
}