zoj 2818 Root of the Problem

Root of the Problem

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Time Limit: 2 Seconds      Memory Limit: 65536 KB

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Given positive integers B and N, find an integer A such that A^N is as close as possible to B. (The result A is an approximation to the Nth root of B.) Note that A^N may be less than, equal to, or greater than B.

Input: The input consists of one or more pairs of values for B and N. Each pair appears on a single line, delimited by a single space. A line specifying the value zero for both B and N marks the end of the input. The value of B will be in the range 1 to 1,000,000 (inclusive), and the value of N will be in the range 1 to 9 (inclusive).

Output: For each pair B and N in the input, output A as defined above on a line by itself.

 #include <iostream>
 #include <cmath>
 #include <cstdlib>
 using namespace std;
 int main(){
     double b, n;
     while(cin >> b >> n){
         if(b ==  && n == )
             break;
         //pow:double pow(double, double)
         int a = (int)pow(b, / n);//直接取整，不是四舍五入 ,pow(a, n) < b
         if(b - pow(a, n) < pow(a + , n) - b)
             cout << a << endl;
         else
             cout << a +  << endl;
     }
     return ;
 }

Example Input:	Example Output:
4 3 5 3 27 3 750 5 1000 5 2000 5 3000 5 1000000 5 0 0	1 2 3 4 4 4 5 16