Update addTwoNumbers.md

Author: ps0305

leetcode/add-two-numbers/addTwoNumbers.md

@@ -5,7 +5,7 @@ Approach : Elementary Math
 Algorithm
 
 Just like how you would sum two numbers on a piece of paper, 
-we begin by summing the least-significant digits, which is the head of l1 and l2. Since each digit is in the range of 0 \ldots 90…9, summing two digits may "overflow". For example 5 + 7 = 125+7=12. In this case, we set the current digit to 22 and bring over the carry = 1carry=1 to the next iteration. carrycarry must be either 00 or 11 because the largest possible sum of two digits (including the carry) is 9 + 9 + 1 = 199+9+1=19.
+we begin by summing the least-significant digits, which is the head of l1 and l2. Since each digit is in the range of 0 \ldots 90…9, summing two digits may "overflow". For example 5 + 7 = 12. In this case, we set the current digit to 2 and bring over the carry = 1 to the next iteration. carrycarry must be either 0 or 1 because the largest possible sum of two digits (including the carry) is 9 + 9 + 1 = 199+9+1=19.
 
 The pseudocode is as following: