def add_40_digits(str1, str2):
max_digits = 40
# Convert str1 into a 40 decimal digit value
num1 = [0] * max_digits
for i, c in enumerate(reversed(str1)):
num1[i] = int(c) - int('0')
# Convert str2 into a 40 decimal digit value
num2 = [0] * max_digits
i = 0
for i, c in enumerate(reversed(str2)):
num2[i] = int(c) - int('0')
i = i + 1
# Sum the digits at each position and record the carry for each position
sum = [0] * max_digits
carry = [0] * max_digits
for i in range(max_digits):
(sum[i],
carry[i]) = Ex__1_single_digit_adder.add_digits(num1[i], num2[i])
# Ripple the carry values across the digits
for i in range(max_digits - 1):
if (carry[i] == 1):
sum[i + 1] = (sum[i + 1] + 1) % 10
if (sum[i + 1] == 0):
carry[i + 1] = 1
# Convert the result into a string with leading zeros removed
sum.reverse()
sum_str = "".join(map(str, sum))
sum_str = sum_str.lstrip('0') or '0'
return sum_str
def test_1(self):
self.assertEqual(Ex__1_single_digit_adder.add_digits(0, 0), (0, 0))
def test_7(self):
self.assertEqual(Ex__1_single_digit_adder.add_digits(9, 9), (8, 1))
def test_6(self):
self.assertEqual(Ex__1_single_digit_adder.add_digits(9, 1), (0, 1))
def test_4(self):
self.assertEqual(Ex__1_single_digit_adder.add_digits(1, 2), (3, 0))