[leetcode]Happy Number C语言

【题目】

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

【题目分析】

这道题关键是当一个数不是happy number的时候的判断，因为如果不及时返回false,那么就会一直处于死循环的状态。用数组来存储中间值，当中间值多次出现时，我们把它理解为陷入死循环了，此时返回false;

【具体代码如下】

int nn(int n)
{
int total=0;
int i=n/10;
int j=n%10;
while(i>0)
{
total+=j*j;

j=i%10;
i=i/10;
}
total+=j*j;

return total;
}
int  isHappy(int n) {
int happy=nn(n);
int hash[370]={0};
while((happy!=1))
{
if(happy<=1000)
{
hash[happy]++;
if(hash[happy]>10)
return false;
}
happy=nn(happy);
}
return true;
}

【个人总结】

这道题在hash数组的大小上有待研究，通过测试，大小的临界值为367，凡是大于等于367的，都能AC,小于的都不能通过。这应该跟测试的数据有关，测试的数据影响中间值，中间值存放在hash数组中。从另一个方面来看，从int型数的最大取值上来看，hash的大小应该更大些。