Question

我正在尝试找出以下问题的实现：

从未排序的链接列表中删除重复项。

我的方法是尝试遍历链表。在每个节点上，检查哈希表以查看它是否存在。如果是，请删除该节点。否则，插入列表。

我的链表实施：

struct Node {
    int data;
    Node *next;
    Node(int d){data = d;}
};

class LinkedList {
private:
    Node *head;
public:
    LinkedList() {head = NULL;}
    ~LinkedList() {
        while (head != NULL) {
            Node *tmp = head;
            head = head->next;
            delete tmp;
        }
    }
    void add(int d) {
        Node *newNode = new Node(d);
        newNode->next = head;
        head = newNode;
    }
    void print() {
        Node *cur = head;
        while (cur != NULL) {
            std::cout << cur->data << "->";
            cur = cur->next;
        }
    }
    Node *getHead() {
        return head;
    }
};

哈希表：

class HashNode {
protected:
    int key;
    int value;
    HashNode *next;
public:
    HashNode(int key, int value) {
        this->key = key;
        this->value = value;
        this->next = NULL;
    }
    friend class HashMap;
};

class HashMap {
private:
    HashNode **htable;
public:
    HashMap() {
        htable = new HashNode*[tableSize];
        for (int i = 0; i < tableSize; i++) {
            htable[i] = NULL;
        }
    }
    ~HashMap() {
        for (int i = 0; i < tableSize; i++) {
            HashNode *entry = htable[i];
            while (entry != NULL) {
                HashNode *prev = entry;
                entry = entry->next;
                delete prev;
            }
            delete[] htable;
        }
    }
    int hashFunction(int key) {
        return key % tableSize;
    }
    void insert(int key, int value) {
        int hashVal = hashFunction(key);
        HashNode *prev = NULL;
        HashNode *entry = htable[hashVal];
        while (entry != NULL) {
            prev = entry;
            entry = entry->next;
        }
        entry = new HashNode(key, value);
        if (prev == NULL) {
            htable[hashVal] = entry;
        } else {
            prev->next = entry;
        }
    }
    bool search(int key) {
        bool flag = false;
        int hashVal = hashFunction(key);
        HashNode *entry = htable[hashVal];
        while (entry != NULL) {
            if (entry->key == key)
                flag = true;
            entry = entry->next;
        }
        return flag;
    }
};

最后我的功能是删除重复项：

void removeDuplicates(LinkedList *listPtr, HashMap *hashPtr) {
    Node *cur = listPtr->getHead();
    Node *prev = NULL;
    while (cur != NULL) {
        Node *tmp = cur;
        if (hashPtr->search(cur->data)) {
            prev->next = cur->next;
            cur = cur->next;
            delete tmp;
        } else {
            hashPtr->insert(cur->data, 1);
            prev = cur;
            cur = cur->next;
        }
    }
}

当我在main中运行以下内容时：

#include <iostream>
const int tablesize = 128;
int main() {
    LinkedList myList;
    HashMap intMap;
    myList.add(1);
    myList.add(3);
    myList.add(5);
    myList.add(3);
    myList.add(3);
    myList.add(5);
    myList.add(20);
    myList.add(57);
    std::cout << "before function call: \n";
    myList.print();
    removeDuplicates(&myList, &intMap);
    std::cout << "\nafter:\n";
    myList.print();

    return 0;
}

这是我得到的输出：

before function call: 
57->20->5->3->3->5->3->1->
after:
go(14453,0x7fff762c1300) malloc: *** error for object 0x7f9250801200: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
57->20->5->3->1->Abort trap: 6

最终列表正确打印出来，但我仍然遇到与之相关的奇怪错误。可以有人帮助我，给新手一些提示我做错了什么，提前谢谢。

编辑 - 我在gdb下运行它，这是输出：

main () at 2.1RemoveDuplicatesFromLinkedList.cpp:149
149     std::cout << "\nafter:\n";
(gdb) step
57->20->5->3->3->5->3->1->
after:
150     myList.print();
(gdb) step
152     return 0;
(gdb) step
broken(14784,0x7fff762c1300) malloc: *** error for object 0x100801200: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
57->20->5->3->1->
Program received signal SIGABRT, Aborted.
0x00007fff8484e286 in __pthread_kill () from /usr/lib/system/libsystem_kernel.dylib
(gdb)

奇怪的是，我很好奇所以我去了cpp.sh在线编译和执行。输出完全符合预期，程序终止没有任何错误。在我的本地机器上有什么可能导致这种情况的想法？（OS X）

正在释放的指针未分配（从未排序的链表中删除重复项 - c ++）

0 个答案: