Vishal Balasubramanian’s Post

LeetCode Progress | 258. Add Digits (Python) Today I solved “Add Digits” on LeetCode. Problem: Given an integer num, repeatedly add its digits until the result has only one digit, and return it. My approach: I used an iterative digit-sum process. -- Repeatedly extracted digits using modulo and division -- Summed the digits until the number became a single digit -- Returned the final value Optimal approach (O(1) without loops): This problem follows the mathematical concept of a Digital Root. The result can be found using: -- If num == 0, return 0 -- Otherwise, return 1 + (num - 1) % 9 This avoids iteration entirely and runs in constant time. What I learned: -- Some problems that look iterative have hidden mathematical patterns -- Recognizing number properties (like digital roots) can lead to O(1) solutions -- Always look for a formula when repeated digit operations are involved #leetcode #python #dsa #datastructures #algorithms #coding #programming #problemSolving #softwareengineering #computerscience #interviewprep #codinginterview #100daysofcode #pythonprogramming

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