258. Add Digits

LeetCodeMathSimulationNumber TheoryOpen on judge ↗

Given an integer num, repeatedly add all its digits until the result has only one digit, and return it. Example 1: Input: num = 38 Output: 2 Explanation: The process is 38 --> 3 + 8 --> 11 11 --> 1 + 1 --> 2 Since 2 has only one digit, return it. Example 2: Input: num = 0 Output: 0 Constraints: - 0 <= num <= 231 - 1 Follow up: Could you do it without any loop/recursion in O(1) runtime

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solution.cppC++17

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