Range Sum of Linked List

docs/linked-list/range-sum-of-linked-list.md

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+---
+id: range-sum-of-linked-list
+title: Range Sum of Linked List
+sidebar_label: Range Sum of Linked List
+description: 'Calculate the sum of node values within this range.'
+tags: [dsa, data-structures, LinkedList]
+---
+
+### Range Sum of Linked List
+
+Given a linked list and a range defined by start and end (0-indexed), calculate the sum of the node values within this range.
+
+### Implementation in c++
+
+```cpp
+#include <iostream>
+using namespace std;
+
+struct ListNode {
+    int val;
+    ListNode* next;
+    ListNode(int x) : val(x), next(NULL) {}
+};
+
+int rangeSum(ListNode* head, int start, int end) {
+    int rangeSum = 0;         // Sum of values within the range
+    int position = 0;          // Track the current position in the list
+    ListNode* current = head;  // Pointer to traverse the list
+
+    // Traverse the linked list
+    while (current != nullptr) {
+        // If the position is within the specified range, add to sum
+        if (position >= start && position <= end) {
+            rangeSum += current->val;
+        }
+
+        // Break if we've passed the end of the range
+        if (position > end) {
+            break;
+        }
+
+        // Move to the next node and increment the position
+        current = current->next;
+        position++;
+    }
+
+    return rangeSum;
+}
+
+int main() {
+    // Creating a sample linked list: 1 -> 2 -> 3 -> 4 -> 5
+    ListNode* head = new ListNode(1);
+    head->next = new ListNode(2);
+    head->next->next = new ListNode(3);
+    head->next->next->next = new ListNode(4);
+    head->next->next->next->next = new ListNode(5);
+
+    // Calculate the sum of node values from position 1 to 3 (inclusive)
+    int start = 1;
+    int end = 3;
+    cout << "Range Sum: " << rangeSum(head, start, end) << endl;  // Output should be 2 + 3 + 4 = 9
+
+    // Clean up the memory allocated for the linked list
+    ListNode* temp;
+    while (head != nullptr) {
+        temp = head;
+        head = head->next;
+        delete temp;
+    }
+
+    return 0;
+}
+```
+
+### Complexity
+
+- **Time Complexity**: $O(n)$
+- **Space Complexity**: $O(1)$