202 Happy Number

202 Happy Numberquestion

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

Idea

The data of type int has 10 digits, the maximum value is , the sum of squares is, so an array of 810 size can be expressed so that the sum of squares may be computed.

Give an n value, first calculate the sum of squares of the number of this n, if this and previous occurrence (M==n also appears), then this number is not happy numbers.

Reason: If A number is happy, then all members of the its sequence are happy; If a number is unhappy, all members of the sequence are unhappy.
If a count is happy number, then the order of his numbers is reversed, and the new number is still happy. Likewise, if not, no matter how reversed, it is not happy number. If calculated and previously calculated, then this step is from that and counted, now from this and then calculate the words, and then back, is an infinite cycle.

Code

BOOL Ishappy (intN{bool hash[810] = {false}; Intm=N; while(1) {intsum= 0; while(m) {sum+= (m% 10) * (m% 10);m/= 10; }if(sum= = 1)returnTrueElse if(hash[sum] ||m==N)returnFalse hash[sum] = true;m=sum; }returnfalse;}

202 Happy Number