Leetcode 202:happy Number

Write an algorithm to determine if a 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'll stay), or it loops Endl essly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy.

Example:19 is a happy number 12 + 92 = 82 82 + 22 = 68 62 + 82 = 100 12 + 02 + 02 = 1 Analysis: First we need to compute the numbers n every square sum, this is relatively simple, the code is as follows:

int countn (int n) {
        int tmp = n;
        int sum = 0;
        while (tmp > 0) {
            int result = tmp%;
            sum + = result * result;
            TMP = TMP/10;
        }
        return sum;
    }

Then there is the main part of the function, which should be noted that loops may occur, such as: 2, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37 ... So we need to use a set of all the occurrences of N and Countn are recorded, so that the recurrence of time to stop the execution of the program to avoid a dead loop. Map is a better choice because the complexity of the lookup element is O (1). The main part of the code is as follows:

    BOOL Ishappy (int n) {
        map<int, int> int_map;
        if (n==1) {return
            true;
        }
        int sum = 0;
        while (n!= 1) {
            Int_map.insert (pair<int, int> (n, N));
            sum = COUNTN (n);
            if (sum ==1) {return
                true;
            }
            if (Int_map.count (sum)) return
                false;
            n = sum;
        }
        return true;
    }