[Leetcode]: 202:happy number

Topic:

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

Analysis:

The difficulty of this problem or read the question, and did not understand the needs of the topic

The title asks for any positive integer, continuously the sum of squares of the numbers on each digit, and if the final convergence is 1, the number is happy numbers, or the program may start to loop from a certain number.

We only use the rules to calculate the problem, use HashSet to store the results, so we can judge whether the result is in the loop

Code:

     Public BooleanIshappy (intN) {if(n<=0){            return false; }         LongLnresult =N; Set<Long> set =NewHashset<long>();  while(lnresult<=integer.max_value) {Lnresult=Digitsquare (Lnresult); if(Lnresult = = 1){                return true; }                         if(Set.contains (Lnresult)) {return false; } Else{set.add (lnresult); }        }          return false; }            Private LongDigitsquare (Longlninput) {          LongSum = 0;  while(lninput!=0) {Sum+ = Math.pow (lninput%10, 2); Lninput/= 10; }          returnSum; }

[Leetcode]: 202:happy number