leetcode_202题——Happy Number(哈希)
2015-05-05 09:13
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Happy Number
Total Accepted: 7315 Total Submissions: 22724My SubmissionsQuestion Solution
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
Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.
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这道题将每次根据前一个值计算出来的结果储存在set中,再进行查找就可以了
#include<iostream> //#include<map> #include<set> using namespace std; int n_to_n(int a) { int b=a; int last_result=0; while(b!=0) { last_result=(b%10)*(b%10)+last_result; b=b/10; } return last_result; } bool isHappy(int n) { set<int> temp; temp.insert(n); int a=n; bool c; while(1) { int b=n_to_n(a); if(b==1) { c=1; break; } if(temp.count(b)==1) { c=0; break; } temp.insert(b); cout<<b<<endl; a=b; } return c; } int main() { cout<<isHappy(2)<<endl; }
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