Leetcode 202 Happy Number

Problem:

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:19 is a happy number

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

Summary:

If the sum of squares and sums of the individual bits of an integer is repeated this operation is 1, then this number is happy. Give a number n to determine if it is happy.

Analysis:

A number repeats the sum of the squares and the sum of the operations of 1 is happy number, then the judge is not the basis of happy numbers, then the number of single-digit square and add no matter how many times, still cannot be 1. Then there must be a number of loops in the process of addition, 1 is not included in the loop.

So simply repeat the sum of squares and operations, determine the sum of each number of bits squared and after the result has not appeared, if never appear, then continue to calculate, otherwise judge this number is not happy.

1 classSolution {2  Public:3     BOOLIshappy (intN) {4unordered_map<int,int>m;5          while(true) {6             intsum =0;7              while(n) {8Sum + = (nTen) * (n%Ten);9N/=Ten;Ten             } One              An =sum; -             if(m[sum]++ >0) { -                  Break; the             } -         } -          -         returnn = =1; +     } -};

Leetcode 202 Happy Number