# Check if elements of Linked List are present in pair in Python

PythonServer Side ProgrammingProgramming

Suppose we have a singly linked list. We have to check whether each element in the given linked list is present in a pair, in other words all elements occur even no. of times.

So, if the input is like list = [2,5,5,2,3,3], then the output will be True.

To solve this, we will follow these steps −

• while current_node is not null, do
• xor_res := xor_res XOR value of current_node
• current_node := next of current_node
• return False when xor_res is non-zero otherwise True

## Example

Let us see the following implementation to get better understanding −

Live Demo

class ListNode:
def __init__(self, data, next = None):
self.val = data
self.next = next
def make_list(elements):
for element in elements[1:]:
while ptr.next:
ptr = ptr.next
ptr.next = ListNode(element)
xor_res = 0
while current_node != None:
xor_res = xor_res ^ current_node.val
current_node = current_node.next
return False if xor_res else True
print(solve(head))
[2,5,5,2,3,3]
True