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Program to find numbers represented as linked lists in Python
Suppose we have two singly linked list L1 and L2, each representing a number with least significant digits first, we have to find the summed linked list.
So, if the input is like L1 = [5,6,4] L2 = [2,4,8], then the output will be [7, 0, 3, 1, ]
To solve this, we will follow these steps:
carry := 0
res := a new node with value 0
curr := res
while L1 is not empty or L2 is not empty or carry is non-zero, do
l0_val := value of L1 if L1 is not empty otherwise 0
l1_val := value of L2 if L2 is not empty otherwise 0
sum_ := l0_val + l1_val
carry := quotient of (sum_ + carry) / 10
add_val := remainder of (sum_ + carry) / 10
curr.next := a new node with value add_val
curr := next of curr
L1 := next of L1 if L1 is not empty otherwise null
L2 := next of L2 if L2 is not empty otherwise null
next of curr := null
return next of res
Let us see the following implementation to get better understanding:
Example
class ListNode:
def __init__(self, data, next = None):
self.val = data
self.next = next
def make_list(elements):
head = ListNode(elements[0])
for element in elements[1:]:
ptr = head
while ptr.next:
ptr = ptr.next
ptr.next = ListNode(element)
return head
def print_list(head):
ptr = head
print('[', end = "")
while ptr:
print(ptr.val, end = ", ")
ptr = ptr.next
print(']')
class Solution:
def solve(self, L1, L2):
carry = 0
res = ListNode(0)
curr = res
while L1 or L2 or carry:
l0_val = L1.val if L1 else 0
l1_val = L2.val if L2 else 0
sum_ = l0_val + l1_val
carry, add_val = divmod(sum_ + carry, 10)
curr.next = ListNode(add_val)
curr = curr.next
L1 = L1.next if L1 else None
L2 = L2.next if L2 else None
curr.next = None
return res.next
ob = Solution()
L1 = make_list([5,6,4])
L2 = make_list([2,4,8])
print_list(ob.solve(L1, L2))Input
[5,6,4], [2,4,8]
Output
[7, 0, 3, 1, ]
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