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Solve several coding interview problems

GoogleSoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenCoding & Algorithms

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This problem tests your ability to perform string-based arithmetic and handle edge cases in digit-by-digit computation.

Problem: String-Based Addition of Large Numbers

Given two non-negative integers represented as strings num1 and num2, return the sum of the two numbers as a string. You cannot convert the input strings directly to integers (e.g., using int() in Python or parseInt in JS), as the numbers might exceed the maximum capacity of standard integer types.

Constraints

  • num1.length and num2.length are between 1 and 10,000.
  • num1 and num2 consist of digits '0'-'9'.
  • num1 and num2 do not contain any leading zeros except for the number "0" itself.

Examples

Example 1: Input: num1 = "11", num2 = "123" Output: "134"

Example 2: Input: num1 = "456", num2 = "77" Output: "533"

Example 3: Input: num1 = "0", num2 = "0" Output: "0"

Implementation

def addStrings(num1: str, num2: str) -> str:
    # Write your code here

Hints

Hint 1

Start from the last character of each string, representing the least significant digit, and use pointers to move backwards.

Hint 2

Maintain a variable to keep track of the carry as you add corresponding digits from each string.

Hint 3

If one string is longer than the other, continue adding the remaining digits and the carry until all digits are processed.

Follow-up questions

  • How would you modify your approach if the numbers were allowed to be negative?
  • How would you perform subtraction for two large numbers represented as strings?
  • What is the time and space complexity of your solution, and can you optimize the space if the strings are extremely large?