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add_two_nums.py
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add_two_nums.py
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#!/usr/bin/env python
'''
Leetcode: Add Two Numbers
You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
'''
from __future__ import division
import random
class DigitNode(object):
def __init__(self, digit, next=None):
self.digit = digit
self.next = next
def __str__(self):
if next:
return 'DigitNode(%d, %s)' % (self.digit, str(self.next))
else:
return 'DigitNode(%d)' % (self.digit)
def add_two_numbers(a, b):
prev_carry = 0
orig_node = None
prev_node = None
while a and b:
digit = (a.digit + b.digit + prev_carry) % 10
cur_carry = (a.digit + b.digit + prev_carry) // 10
node = DigitNode(digit)
if prev_node: prev_node.next = node
else: orig_node = node
a = a.next
b = b.next
prev_carry = cur_carry
prev_node = node
# leftover
x = a if a else b
while x:
digit = (x.digit + prev_carry) % 10
cur_carry = (x.digit + prev_carry) // 10
node = DigitNode(digit)
if prev_node: prev_node.next = node
x = x.next
prev_carry = cur_carry
prev_node = node
return orig_node
if __name__ == '__main__':
a = DigitNode(2, DigitNode(4, DigitNode(3, DigitNode(5))))
b = DigitNode(5, DigitNode(6, DigitNode(4, DigitNode(1, DigitNode(2)))))
print add_two_numbers(a,b)