Merge branch 'master' of https://github.com/jbcodeforce/python-code

algorithms/add_two_numbers.py

@@ -0,0 +1,71 @@
+"""
+given two non-empty linked lists representing two non-negative integers. 
+The digits are stored in reverse order, and each of their nodes contains a single digit. 
+dd the two numbers and return the sum as a linked list.
+
+You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+
+Input: l1 = [2,4,3], l2 = [5,6,4]
+Output: [7,0,8]
+Explanation: 342 + 465 = 80
+
+> assume n1 and n2 has the same number of digits
+"""
+
+from typing import Optional
+
+class ListNode:
+    def __init__(self,val=0, next=None):
+        self.value = val
+        self.next = next
+
+    def __str__(self):
+        head=self
+        s = "["
+        while head != None:
+            s+=str(head.value) + ','
+            head=head.next
+        return s[:-1]+']'
+
+
+def add_two_numbers(head1: Optional[ListNode], head2: Optional[ListNode]) -> Optional[ListNode]:
+    resultHead = ListNode()
+    n3_ptr= resultHead
+    n3_pptr = n3_ptr
+    while head1 is not None or head2 is not None:
+        d2 = head2.value if head2 != None else 0
+        d1 = head1.value if head1 != None else 0
+        n3_ptr.value += d1 + d2
+        head1 = head1.next if head1 != None else None
+        head2 = head2.next if head2 != None else None
+
+        n3_ptr.next = ListNode()
+
+        if n3_ptr.value > 9:
+            n3_ptr.value = n3_ptr.value -10
+            n3_ptr.next.value = 1
+        n3_pptr = n3_ptr
+        n3_ptr = n3_ptr.next
+    if n3_ptr.value == 0:
+        n3_pptr.next=None
+    return resultHead
+
+l1=ListNode(2, ListNode(4,ListNode(3)))
+l2=ListNode(5, ListNode(6,ListNode(4)))
+
+r = add_two_numbers(l1,l2)
+print(r)
+assert str(r) == "[7,0,8]"
+r = add_two_numbers(ListNode(0),ListNode(0))
+print(r)
+assert str(r) == "[0]"
+# assert add_two_numbers(l1,l2) == [7,0,8]
+l1=ListNode(9, ListNode(9,ListNode(9,ListNode(9,ListNode(9,ListNode(9, ListNode(9)))))))
+l2=ListNode(9, ListNode(9,ListNode(9,ListNode(9))))
+r = add_two_numbers(l1,l2)
+print(r)
+assert str(r) == "[8,9,9,9,0,0,0,1]"
+r = add_two_numbers(l2,l1)
+print(r)
+assert str(r) == "[8,9,9,9,0,0,0,1]"
+