Add two numbers represented by linked lists

Author: anantkaushik

Python/GeeksforGeeks/add-two-numbers-represented-by-linked-lists.py

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+"""
+Problem Link: https://practice.geeksforgeeks.org/problems/add-two-numbers-represented-by-linked-lists/1
+
+Given two numbers represented by two linked lists of size N and M. The task is to return a sum list. 
+The sum list which is a linked list representation of addition of two input numbers.
+
+Input:
+First line of input contains number of testcases T. For each testcase, first line of input 
+contains length of first linked list and next line contains N elements of the linked list. 
+Again, next line contains M, and following line contains M elements of the linked list.
+
+Output:
+Output the resultant linked list.
+
+User Task:
+The task is to complete the function addTwoLists() which has node reference of both the 
+linked lists and returns the head of new list.
+
+Constraints:
+1 <= T <= 100
+1 <= N, M <= 100
+
+Example:
+Input:
+2
+2
+4 5
+3
+3 4 5
+2
+6 3
+1
+7
+
+Output:
+0 9 3 
+0 7
+
+Explaination:
+5->4 // linked list repsentation of 45.
+5->4->3 // linked list representation of 345.
+0->9 ->3 // linked list representation of 390 resultant linked list.
+"""
+import atexit
+import io
+import sys
+_INPUT_LINES = sys.stdin.read().splitlines()
+input = iter(_INPUT_LINES).__next__
+_OUTPUT_BUFFER = io.StringIO()
+sys.stdout = _OUTPUT_BUFFER
+@atexit.register
+def write():
+    sys.__stdout__.write(_OUTPUT_BUFFER.getvalue())
+    
+# Node Class
+class Node:
+    def __init__(self, data):   # data -> value stored in node
+        self.data = data
+        self.next = None
+# Linked List Class
+class LinkedList:
+    def __init__(self):
+        self.head = None
+    # creates a new node with given value and appends it at the end of the linked list
+    def append(self, new_value):
+        new_node = Node(new_value)
+        if self.head is None:
+            self.head = new_node
+            return
+        curr_node = self.head
+        while curr_node.next is not None:
+            curr_node = curr_node.next
+        curr_node.next = new_node
+# prints the elements of linked list starting with head
+def printList(head):
+    if head is None:
+        print(' ')
+        return
+    curr_node = head
+    while curr_node:
+        print(curr_node.data,end=" ")
+        curr_node=curr_node.next
+    print(' ')
+if __name__ == '__main__':
+    t=int(input())
+    for cases in range(t):
+        n_a = int(input())
+        a = LinkedList() # create a new linked list 'a'.
+        nodes_a = list(map(int, input().strip().split()))
+        nodes_a = nodes_a[::-1] # reverse the input array
+        for x in nodes_a:
+            a.append(x)  # add to the end of the list
+        n_b =int(input())
+        b = LinkedList()  # create a new linked list 'b'.
+        nodes_b = list(map(int, input().strip().split()))
+        nodes_b = nodes_b[::-1]  # reverse the input array
+        for x in nodes_b:
+            b.append(x)  # add to the end of the list
+        result_head = addBoth(a.head,b.head)
+        printList(result_head)
+''' This is a function problem.You only need to complete the function given below '''
+#User function Template for python3
+'''
+	Function to add two numbers represented 
+	in the form of the linked list.
+	
+	Function Arguments: head_a and head_b (heads of both the linked lists)
+	Return Type: head of the resultant linked list.
+    
+    __>IMP : numbers are represented in reverse in the linked list.
+    Ex:
+        145 is represented as  5->4->1.
+    
+    resultant head is expected in the same format.
+    
+# Node Class
+class Node:
+    def __init__(self, data):   # data -> value stored in node
+        self.data = data
+        self.next = None
+'''
+def addBoth(head_a,head_b):
+    #code here
+    res = Node(0)
+    cur = res
+    carry = 0
+    while head_a or head_b:
+        x = head_a.data if head_a else 0
+        y = head_b.data if head_b else 0
+        summ = carry + x + y
+        carry = summ // 10
+        cur.next = Node(summ%10)
+        cur = cur.next
+        if head_a:
+            head_a = head_a.next
+        if head_b:
+            head_b = head_b.next
+    if carry > 0:
+        cur.next = Node(carry)
+    return res.next