Add One To Number: Interviewbit Solution

Problem: Add One To Number

Problem Description:

Given a non-negative number represented as an array of digits,

add 1 to the number ( increment the number represented by the digits ).

The digits are stored such that the most significant digit is at the head of the list.

Example:

If the vector has [1, 2, 3]
 the returned vector should be [1, 2, 4]
 as 123 + 1 = 124.

Solution: