1.求n的所有因子,循环枚举到sqrt(n):
int arr[100] = {1}; //1是任意数字的因子
//用数组按顺序存储因子,函数返回因子的个数
int factor(int n) {
int count = 1, num = sqrt(n);
for (int i = 2; i <= num; i++) {
if ((n % i == 0) && (n != i * i)) {
arr[count++] = i;
arr[count++] = n / i;
}
}
if (n == (num*num)) arr[count++] = num;
return count;
}