问题描述：
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
public class Q3 {
/// <summary>
/// 取得最大的质因数
/// </summary>
/// <param name="max">The max.</param>
/// <returns></returns>
public static long q3(long max) {
//遍历可能的质因数2 到。。
List<long> math = new List<long>();
for (long i = 2;max != 1; i++) {
while (max % i == 0) {
math.Add(i);
max = max / i;
}
}
return math.Distinct().Max();
}
public static void test() {
var t1 = DateTime.Now;
Console.WriteLine(" " + q3(600851475143) + " cast time " + (DateTime.Now - t1).TotalSeconds);
}
}
