# Find the product of first k nodes of the given Linked List in C++

Consider we have few elements in a linked list. We have to find the multiplication result of first k number of elements. The value of k is also given. So if the list is like [5, 7, 3, 5, 6, 9], and k = 3, then result will be 5 * 7 * 3 = 105.

The processes is straight forward. We simply read the current element starting from left side, then multiply it with the prod. (initially prod is 1), when k number of elements are traversed, then stop.

## Example

#include<iostream>
#include<cmath>
using namespace std;
class Node{
public:
int data;
Node *next;
};
Node* getNode(int data){
Node *newNode = new Node;
newNode->data = data;
newNode->next = NULL;
return newNode;
}
void append(struct Node** start, int key) {
Node* new_node = getNode(key);
Node *p = (*start);
if(p == NULL){
(*start) = new_node;
return;
}
while(p->next != NULL){
p = p->next;
}
p->next = new_node;
}
long long prodFirstKElements(Node *start, int k) {
long long res = 1;
int count = 0;
Node* temp = start;
while (temp != NULL && count != k) {
res *= temp->data;
count++;
temp = temp->next;
}
return res;
}
int main() {
Node *start = NULL;
int arr[] = {5, 7, 3, 5, 6, 9};
int n = sizeof(arr)/sizeof(arr[0]);
int k = 3;
for(int i = 0; i<n; i++){
append(&start, arr[i]);
}
cout << "Product of first k elements: " << prodFirstKElements(start, k);
}

## Output

Product of first k elements: 105