Create add1.py

add1.py

@@ -0,0 +1,57 @@
+# Python program to add one to a linked list
+
+class Node:
+    def __init__(self, data):
+        self.data = data
+        self.next = None
+
+# Recursively add 1 from end to beginning and return
+# carry after all nodes are processed.
+def addWithCarry(head):
+
+    # If linked list is empty, return carry
+    if head is None:
+        return 1
+
+    # Add carry returned by the next node call
+    res = head.data + addWithCarry(head.next)
+
+    # Update data and return new carry
+    head.data = res % 10
+    return res // 10
+
+def addOne(head):
+
+    # Add 1 to linked list from end to beginning
+    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:
+        newNode = Node(carry)
+        newNode.next = head
+
+        # New node becomes head now
+        return newNode
+
+    return head
+
+def printList(head):
+    curr = head
+    while curr:
+        print(curr.data, end=" ")
+        curr = curr.next
+    print()
+
+if __name__ == "__main__":
+
+    # Create a hard-coded linked list:
+    # 1 -> 9 -> 9 -> 9
+    head = Node(1)
+    head.next = Node(9)
+    head.next.next = Node(9)
+    head.next.next.next = Node(9)
+
+    head = addOne(head)
+
+    printList(head)