Create Add1_linkedList.cpp

Add1_linkedList.cpp

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+// C++ program to add one to a linked list
+
+#include <iostream>
+using namespace std;
+
+class Node {
+  public:
+    int data;
+    Node *next;
+
+    Node(int x) {
+           data = x;
+        next = nullptr;
+    }
+};
+
+// Recursively add 1 from end to beginning and return
+// carry after all nodes are processed.
+int addWithCarry(Node *head) {
+
+    // If linked list is empty, return carry
+    if (head == nullptr) {
+        return 1;
+    }
+
+    // Add carry returned by the next node call
+    int res = head->data + addWithCarry(head->next);
+
+    // Update data and return new carry
+    head->data = res % 10;
+    return res / 10;
+}
+
+Node *addOne(Node *head) {
+
+    // Add 1 to linked list from end to beginning
+    int carry = addWithCarry(head);
+
+    // If there is carry after updating all nodes,
+    // then we need to add a new node to the linked list
+    if (carry) {
+        Node *newNode = new Node(carry);
+        newNode->next = head;
+
+          // New node becomes head now
+          return newNode; 
+    }
+
+    return head;
+}
+
+void printList(Node *head) {
+    Node *curr = head;
+    while (curr != nullptr) {
+        cout << curr->data << " ";
+        curr = curr->next;
+    }
+    cout << endl;
+}
+
+int main() {
+
+      // Create a hard-coded linked list:
+    // 1 -> 9 -> 9 -> 9
+    Node *head = new Node(1);
+    head->next = new Node(9);
+    head->next->next = new Node(9);
+    head->next->next->next = new Node(9);
+
+    head = addOne(head);
+
+    printList(head);
+
+    return 0;
+}