Find the Sum of Last N nodes of the Linked List | Linked List | GFG POTD | C++ | Java | Code Kar Lo

Given a single linked list, calculate the sum of the last n nodes.

0:00 Introduction
0:11 Problem Statement
0:43 Explanation
2:51 C++ Code
4:34 AI Review
5:58 Java Code

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[salmaniproductions]

Solved by own with the same approach bas ye difference tha ki, me 1st while loop me hi pure linked list ka sum le iya and then again count-=n kiya or 2nd while loop me while(count) -> sum-=temp->data. kar diya. Thank you bhaiyya.

[Shotnshorts]

We can do this in single traversal using a queue of fixed size (n -> number of end nodes), for each node we add the node->value to sum variable and push the node->value to queue and if queue length exceeds 'n', we pop from front and subtract the popped value from sum.
But this approach increases our space complexity to O(n), n =number of nodes at end.

We can also use a map to store sum but the space complexity of using a map will be O(L), L = length of given list

[dayashankarlakhotia]

public int sumOfLastN_nodes(Node head, int n){
Node prev=0, cur=0;
int cnt=0;
while(prev!=null){
if(cnt>=n){
cur=cur.next;
}
prev=prev.next;
cnt++;
}
int sum=0;
while(cur!=null){
sum+=cur.data;
cur=cur.next;
}
return sum;
}
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