**Find Merge Point of Two Lists**

### Problem Statement :

This challenge is part of a tutorial track by MyCodeSchool Given pointers to the head nodes of 2 linked lists that merge together at some point, find the node where the two lists merge. The merge point is where both lists point to the same node, i.e. they reference the same memory location. It is guaranteed that the two head nodes will be different, and neither will be NULL. If the lists share a common node, return that node's data value. Note: After the merge point, both lists will share the same node pointers. Example In the diagram below, the two lists converge at Node x: [List #1] a--->b--->c \ x--->y--->z--->NULL / [List #2] p--->q Function Description Complete the findMergeNode function in the editor below. findMergeNode has the following parameters: SinglyLinkedListNode pointer head1: a reference to the head of the first list SinglyLinkedListNode pointer head2: a reference to the head of the second list Returns int: the data value of the node where the lists merge Input Format Do not read any input from stdin/console. The first line contains an integer t, the number of test cases.

### Solution :

` ````
Solution in C :
In C++ :
/*
Find merge point of two linked lists
Node is defined as
struct Node
{
int data;
Node* next;
}
*/
int getCount(Node* head)
{
Node* current = head;
int count = 0;
while (current != NULL)
{
count++;
current = current->next;
}
return count;
}
int getNode(int d, Node* head1, Node* head2)
{
int i;
Node* current1 = head1;
Node* current2 = head2;
for(i = 0; i < d; i++)
{
if(current1 == NULL)
{ return -1; }
current1 = current1->next;
}
while(current1 != NULL && current2 != NULL)
{
if(current1 == current2)
return current1->data;
current1= current1->next;
current2= current2->next;
}
return -1;
}
int FindMergeNode(Node *headA, Node *headB)
{
// Complete this function
// Do not write the main method.
int c1 = getCount(headA);
int c2 = getCount(headB);
int d;
if(c1 > c2)
{
d = c1 - c2;
return getNode(d, headA, headB);
}
else
{
d = c2 - c1;
return getNode(d, headB, headA);
}
}
In Java :
/*
Insert Node at the end of a linked list
head pointer input could be NULL as well for empty list
Node is defined as
class Node {
int data;
Node next;
}
*/
int FindMergeNode(Node headA, Node headB) {
// Complete this function
// Do not write the main method.
int countA=0;
int countB=0;
Node tempA=headA;
Node tempB=headB;
while(tempA!=null)
{
countA++;
tempA=tempA.next;
}
while(tempB!=null)
{
countB++;
tempB=tempB.next;
}
int diff=0;
if(countA>countB)
diff=countA-countB;
else
diff=countB-countA;
tempA=headA;
tempB=headB;
if(countA>countB)
{
while(diff >0)
{tempA=tempA.next;
diff--;}
}
else
{while(diff >0)
{ tempB=tempB.next;
diff--;}
}
while(tempA!=null && tempB!=null)
{
tempA=tempA.next;
tempB=tempB.next;
if(tempA==tempB)
return tempA.data;
}
return 0;
}
In python3 :
"""
Find the node at which both lists merge and return the data of that node.
head could be None as well for empty list
Node is defined as
class Node(object):
def __init__(self, data=None, next_node=None):
self.data = data
self.next = next_node
"""
def FindMergeNode(a, b):
h = {}
while a != None:
h[a.data] = a.data
a = a.next
while b != None:
if b.data in h:
return h[b.data]
b = b.next
return None
In C :
// Complete the findMergeNode function below.
/*
* For your reference:
*
* SinglyLinkedListNode {
* int data;
* SinglyLinkedListNode* next;
* };
*
*/
#include <math.h>
int findMergeNode(SinglyLinkedListNode *headA, SinglyLinkedListNode *headB)
{
// Complete this function
// Do not write the main method.
int countA = 0;
int countB = 0;
struct SinglyLinkedListNode *tempHeadA, *tempHeadB;
tempHeadA = headA;
tempHeadB = headB;
while(tempHeadA != NULL){
countA++;
tempHeadA = tempHeadA->next;
}
while(tempHeadB != NULL){
countB++;
tempHeadB = tempHeadB->next;
}
// printf("%d %d", countA,countB);
int biggerNodeExtraNodes = abs(countA - countB);
// printf("%d", biggerNodeExtraNodes);
while(biggerNodeExtraNodes--){
printf("33333333333");
if(countA > countB){
headA = headA->next;
} else{
headB = headB->next;
}
}
while(headA != NULL){
printf("asdfghjklpoiuytredxdcfgh");
if(headA == headB){
return headA->data;
}else{
headA = headA->next;
headB = headB->next;
}
}
return 1;
}
```

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