202. Happy Number (INT)
2015-12-17 08:31
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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, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.
Example: 19 is a happy number
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.
Example: 19 is a happy number
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
class Solution { public: int getSquare(int num){ //because square operation is very often, so enum the result switch(num){ case 0: return 0; case 1: return 1; case 2: return 4; case 3: return 9; case 4: return 16; case 5: return 25; case 6: return 36; case 7: return 49; case 8: return 64; case 9: return 81; } } bool isHappy(int n) { if(n == 0) return false; set<int> squareSum; return dfs(n, squareSum); } bool dfs(int n, set<int>& squareSum){ int tmp; int sum = 0; while(n){ tmp = n%10; sum += getSquare(tmp); n /= 10; } if(sum == 1) return true; else if(squareSum.find(sum)!=squareSum.end()) return false; else { squareSum.insert(sum); return dfs(sum, squareSum); } } };
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