202. Leetcode. Happy number

Source: Internet
Author: User

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process:starting with any positive integer and replace the number by the Sum of the squares of its digits, and repeat the process until the number equals 1 (where it would stay), or it loops Endl essly in a cycle which does not include 1. Those numbers for which this process ends in 1 is happy numbers.

Example: is a happy number

    • 12 + 92 = 82
    • 82 + 22 = 68
    • 62 + 82 = 100
    • 12 + 02 + 02 = 1

Idea: Put a number per bit squared after adding and get a new number, and then continue to do the same for this new number. If you can finally get a 1, the most primitive number is a "Happy". If there is a cycle in the process of not reaching 1, this number is definitely not. Use the set of C + +. Set.count () Determines whether a number is in set, Set.insert (), and inserts an element into the set. A Int_max that represents the largest integer.

202. Leetcode. Happy number

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