In Between Linked Lists

In Between Linked Lists
You are given two linked lists: list1 and list2 of sizes n and m respectively.
Remove list1's nodes from the ath node to the bth node, and put list2 in their place.
Input Format
First line of input contains list1
Second line of input contains two space separated integers representing a and b.
Third line of input contains list2
Constraints
3 <= list1.length <= 10^4
1 <= a <= b < list1.length - 1
1 <= list2.length <= 10^4
Sample Input 1:
0 1 2 3 4 5 -1
3 4
101 102 103 -1
Sample Output 1:
0 1 2 101 102 103 5



////////////////////////////////        code in c++              ////////////////////////////////




class Node {
public:
    int data;
    Node* next;
};
Node *mergeInBetween(Node *list1, int a, int b, Node *list2) 
    {
     Node *tail = list2, *cur = list1, *s,*e;
        while(tail->next) {
            tail = tail->next;
        }
        for(int i = 1; i < a; i++) {
            cur = cur->next;
        }
        s = cur;
        for(int i = 0; i <= b-a; i++) {
            cur = cur->next;
        }
        e = cur;
        s->next = list2;
        tail->next = e->next;
        return list1;
        
}