网易---有道難題---双倍超立方数--Topcoder-編程題(500points)

题目要求：双倍超立方数是指一个正整数可以正好被拆分为两种不同的a^3+b^3的方式，其中a,b均为整数且0<a<=b。对于任何一个指定的 int n, 返回所有的小于等于n的双倍超立方数的个数。

Definition
      Class:  TwiceSuperCubic
Method:  count
Parameters:  int
Returns:  int
Method signature:  int count(int n)
(be sure your method is public)

     
 
Constraints
-  n取值范围为1到1,000,000,000(含)
Examples
0) 
      1

Returns: 0

1) 
      1729

Returns: 1
1729=1^3+12^3
1729=9^3+10^3

2) 
      475574

Returns: 27

 

 

 

 

 

    public static class TwiceSuperCubic
    {
        public static int count(int n)
        {
            int r = 0;
            int f = -1;
            if (n > 0 && n <= 1000000000)
            {
                for (int i = 1; i <= n; i++)
                {
                    f = 0;
                    double sq = Math.Pow(i, 1f / 3);
                    for (int k = 1; k < sq; k++)
                    {
                        if (i > k * k * k)
                        {
                            int m = k;
                            for (; m < sq; m++)
                            {
                                if (i > m * m * m)
                                {
                                    if (i == (m * m * m + k * k * k))
                                    {
                                        f++;
                                    }
                                }
                            }
                        }
                    }
                    if (f > 1)
                    {
                        r++;
                    }
                }
            }
            return r;
        }

    }