Question

我一直在用C ++实现单链表。但是，我正在努力解决在特定节点之后插入节点的功能，以及删除目标节点。我检查了我解析为函数的节点，结果节点甚至没有附加到链表。

struct SNode {
string* element;
SNode *next; // Pointer to the next node

/* Creates a node. */
SNode(string* e, SNode* n)  {
   element = e;
  next = n;
}
string* getElement() { return element; }
void print() { cout << *element; }
};

class SList {
protected:      // data member
SNode* head;
long size;      // number of nodes in the list

public:
/* Default constructor that creates an empty list */
SList() {
    head = NULL;
    size = 0;
}
// ... update and search methods would go here ...
long getSize() { return size; }
int isEmpty() { return size<=0; }

// add a new node to the beginning of the list
SNode* addFirst(string* s) {
    SNode* newNode = new SNode(s, head);
    head = newNode;
    size++;
    return newNode;
}

//remove the first node in the list
string* removeFirst() {
    if (head==NULL) return NULL;
    SNode* node = head;
    head = head->next;
    string* s = node->element;
    node->next = NULL;
    delete node->element;
    size--;
    return s;
}

// insert a new node after node n and store the string s there
void insertAfter (SNode n, string* s) {
    SNode* newNode = new SNode(s, n.next);
    n.print();                       //print out 2
    cout << endl;
    n.next = newNode;
    (n.next)->print();               //print out 6
    cout << endl;
    ((n.next)->next)->print();       //print out 1
    cout << endl;
    size++;
    SNode* iter = head;
    while(iter != NULL){
        if(iter == &n){
            cout << "ok" << endl;
        }
        iter = iter->next;
    }                                 //but not print out "ok"
    print();
    return;
}

// delete node n and return the string stored in n
string* insertAfter (SNode n) {
    SNode* iter = head;
    while(iter != NULL){
        if(iter->next == &n){
            break;
        }
        iter = iter->next;
    }
    iter->next = n.next;
    n.next = NULL;
    string* s = n.element;
    delete n.element;
    size--;
    return s;
}

//display the list's data in order from head to tail
void print() {
    SNode* iter = head;
    while (iter!=NULL) {
        // call SNode method to display iter's data
        iter->print();
        cout << endl;
        iter = iter->next;
    }
    cout << endl;
}

int isNode(SNode n){
    SNode* iter = head;
    while(iter != NULL){
        if(iter == &n){
            return 1;
        }
        iter = iter->next;
    }
    return 0;
}
};

int main(void)
{
   SList* dl = new SList();
   string s1 = "1";
   SNode* p = dl->addFirst(&s1);
   dl->print();

   string s2 = "2";
   //dl->addFirst(&s2);
   SNode* p2 = dl->addFirst(&s2);
   cout << endl;
   dl->print();

   string s3 = "3";
   dl->addFirst(&s3);
   dl->print();

   string s4 = "4";
   dl->addFirst(&s4);
   dl->print();

   string s5 = "5";
   dl->addFirst(&s5);
   dl->print();

   dl->removeFirst();
   dl->print();
   dl->removeFirst();
   dl->print();

   cout << dl->isNode(*p2) << endl;            //still not print "ok"

   string s6 = "6";
   dl->insertAfter((*p2), &s6);
   dl->print();

   return 0;
}

Answer 1

您正在将SNode个对象按值传递给insertAfter()和isNode()，因此对== &n的检查将永远不会是真的。你需要通过指针传递它们。

此外，p2指向列表中的第二个节点，但是在使用现在应该无效的insertAfter()指针调用p2之前，您要从列表中删除2个节点。你实现了一个有效的删除功能，但你没有这样做。

尝试更像这样的东西：

struct SNode { string element; SNode *next; // Pointer to the next node /* Creates a node. */ SNode(string e, SNode *n) { element = e; next = n; } string getElement() { return element; } void print() { cout << element; } }; class SList { protected: // data member SNode* head; long size; // number of nodes in the list public: /* Default constructor that creates an empty list */ SList() { head = NULL; size = 0; } // ... update and search methods would go here ... long getSize() { return size; } int isEmpty() { return (size <= 0); } // add a new node to the beginning of the list SNode* addFirst(string s) { SNode* newNode = new SNode(s, head); head = newNode; size++; return newNode; } //remove the first node in the list string removeFirst() { if (head == NULL) return ""; SNode* node = head; head = node->next; size--; string s = node->element; delete node; return s; } // insert a new node after node n and store the string s there void insertAfter (SNode *n, string s) { SNode* iter = head; while (iter != NULL) { if (iter == n) { break; } iter = iter->next; } if (iter == NULL) { return; } SNode* newNode = new SNode(s, iter->next); iter->next = newNode; size++; } // delete node n and return the string stored in n string removeNode (SNode *n) { SNode *iter = head; SNode *previous = NULL; while (iter != NULL) { if (iter == n) { break; } previous = iter; iter = iter->next; } if (iter == NULL) { return ""; } if (previous != NULL) { previous->next = iter->next; } if (head == iter) { head = iter->next; } size--; string s = iter->element; delete iter; return s; } //display the list's data in order from head to tail void print() { SNode* iter = head; while (iter != NULL) { // call SNode method to display iter's data iter->print(); cout << endl; iter = iter->next; } cout << endl; } bool hasNode(SNode *n) { SNode* iter = head; while (iter != NULL) { if (iter == n) { return true; } iter = iter->next; } return false; } }; int main(void) { SList* dl = new SList(); SNode* p = dl->addFirst("1"); dl->print(); SNode* p2 = dl->addFirst("2"); cout << endl; dl->print(); dl->addFirst("3"); dl->print(); dl->addFirst("4"); dl->print(); dl->addFirst("5"); dl->print(); cout << dl->hasNode(p2) << endl; dl->insertAfter(p2, "6"); dl->print(); dl->removeFirst(); dl->print(); dl->removeFirst(); dl->print(); delete dl; return 0; }

话虽如此，你真的应该使用std::list（或C ++ 11中的std::forward_list）而不是手动实现列表：

#include <list> #include <string> #include <algorithm> //display the list's data in order from head to tail void printString(const std::string &s) { std:::cout << s << std::endl; } void printList(const std::list<std::string> &v) { std::for_each(v.begin(), v.end(), &printString); std::cout << std::endl; } int main(void) { std::list<std::string> dl; dl.push_front("1"); printList(dl); dl.push_front("2"); std::list<std::string>::iterator p2 = dl.begin(); std::cout << std::endl; printList(dl); dl.push_front("3"); printList(dl); dl.push_front("4"); printList(dl); dl.push_front("5"); printList(dl); dl.insert(p2+1, "6"); printList(dl); dl.pop_front(); printList(dl); dl.pop_front(); printList(dl); return 0; }

节点不会附加到链接列表

1 个答案: