通过查找功能在地图中搜索键值没有正确发生

Question

In the code below, I am performing search in map through key value but am not able to get the desired results though common elements are present in both lists and find with map should give expected output. Is there any issues while performing find with map? is that right approach ?

input

list1:10->15->4->20 list2:10->2->4->8

expected output: common->data=4 common->data=10

 #include <iostream>
    #include <stdio.h>
    #include <stdlib.h>
    #include <map>
    using namespace std;
    struct node
    {
        int data;
        struct node* next;
    };
    /* A utility function to insert a node at the beginning of 
       a linked list*/
    void push(struct node** head_ref, int new_data);
    /* A utility function to insert a node at the begining of a linked list*/
    void push (struct node** head_ref, int new_data)
    {
        /* allocate node */
        struct node* new_node =
            (struct node*) malloc(sizeof(struct node));
        /* put in the data */
        new_node->data = new_data;
        /* link the old list off the new node */
        new_node->next = (*head_ref);
        /* move the head to point to the new node */
        (*head_ref) = new_node;
    }
     /*insert the head1 into map and find the head2 in map*/
    int create_hash(struct node* head1,struct node* head2)
    {
      int flag=0;
     map<node*,bool> intersect;

    while(head1!=NULL)
    {
    printf("first_list->data=%d\n",head1->data);
    intersect[head1]=true;
    head1=head1->next;
    }
    while(head2!=NULL)
    {
    printf("second_list->data=%d\n",head2->data);
    if (intersect.find(head2)!= intersect.end())
           printf("common->data=%d\n",head2->data); 
           flag=1;
           head2=head2->next;
    }
    if(flag==1)
    {
    return 0;
    }
    return -1;
    }
    /* Drier program to test above function*/
    int main()
    {
        /* Start with the empty list */
        struct node* head1 = NULL;
        struct node* head2 = NULL;
        int ret_val;
        struct node* unin = NULL;
        /*create a linked lits 10->15->4->20 */
        push (&head1, 20);
        push (&head1, 4);
        push (&head1, 15);
        push (&head1, 10);
        /*create a linked list 10->2->4->8 */
        push (&head2, 10);
        push (&head2, 2);
        push (&head2, 4);
        push (&head2, 8);
        ret_val = create_hash (head1, head2);
        return 0;
    }

Answer 1

You populate the intersect map with pointers to nodes in the first list, and then search that map for pointers to nodes in the second list. Since nodes are not shared between lists, the search will never succeed.

In the context of this implementation, the map should contain the data values, not node pointers.