Add Strings (character array variant)

Problem: Add two big integers represented as character arrays (Add Strings variant) You are given two character arrays a and b, each representing a non-negative integer in base-10 from left to right (e.g. ['1','2','3'] represents 123). Compute the sum of the two numbers and output its decimal representation. Requirements You must not convert the entire input directly into an integer type (e.g. using int() in Python). Perform digit-by-digit addition with carry. Input Format Line 1: a string (no spaces) representing character array a Line 2: a string (no spaces) representing character array b Note: for convenience, the character arrays are provided as plain strings. Output Format Output one line: a string representing a + b. Constraints 1 <= len(a), len(b) <= 1e5 a and b contain only '0'..'9' No leading zeros unless the number is exactly 0 Examples Example 1 Input: 123 77 Output: 200 Example 2 Input: 0 0 Output: 0 Example Input 123 77 Output 200