Find the Merge point of two joined linked lists

https://www.hackerrank.com/challenges/find-the-merge-point-of-two-joined-linked-lists/problem

두 연결 리스트의 연결지점을 찾는 문제

마지막에 return tmp1->data 또는 return tmp2->data 둘다 된다. (어차피 합병 포인트는 같으니까)

int findMergeNode(SinglyLinkedListNode* head1, SinglyLinkedListNode* head2) {
    SinglyLinkedListNode *temp1=head1;
    SinglyLinkedListNode *temp2=head2;
    while(temp1!=temp2){
        if(temp1->next==NULL){
            temp1=head2;
        }
        else {
        temp1=temp1->next;
        }
        if(temp2->next==NULL){
            temp2=head1;
        }
        else{
            temp2=temp2->next;
        }
    }
    return temp2->data;
}

△코드 작성 부분

#include <assert.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* readline();

typedef struct SinglyLinkedListNode SinglyLinkedListNode;
typedef struct SinglyLinkedList SinglyLinkedList;

struct SinglyLinkedListNode {
    int data;
    SinglyLinkedListNode* next;
};

struct SinglyLinkedList {
    SinglyLinkedListNode* head;
    SinglyLinkedListNode* tail;
};

SinglyLinkedListNode* create_singly_linked_list_node(int node_data) {
    SinglyLinkedListNode* node = malloc(sizeof(SinglyLinkedListNode));

    node->data = node_data;
    node->next = NULL;

    return node;
}

void insert_node_into_singly_linked_list(SinglyLinkedList** singly_linked_list, int node_data) {
    SinglyLinkedListNode* node = create_singly_linked_list_node(node_data);

    if (!(*singly_linked_list)->head) {
        (*singly_linked_list)->head = node;
    } else {
        (*singly_linked_list)->tail->next = node;
    }

    (*singly_linked_list)->tail = node;
}

void print_singly_linked_list(SinglyLinkedListNode* node, char* sep, FILE* fptr) {
    while (node) {
        fprintf(fptr, "%d", node->data);

        node = node->next;

        if (node) {
            fprintf(fptr, "%s", sep);
        }
    }
}

void free_singly_linked_list(SinglyLinkedListNode* node) {
    while (node) {
        SinglyLinkedListNode* temp = node;
        node = node->next;

        free(temp);
    }
}

int findMergeNode(SinglyLinkedListNode* head1, SinglyLinkedListNode* head2) {
    SinglyLinkedListNode *temp1=head1;
    SinglyLinkedListNode *temp2=head2;
    while(temp1!=temp2){
        if(temp1->next==NULL){
            temp1=head2;
        }
        else {
        temp1=temp1->next;
        }
        if(temp2->next==NULL){
            temp2=head1;
        }
        else{
            temp2=temp2->next;
        }
    }
    return temp2->data;
}

int main()