poj 1840 Eqs （hash）

题目：http://poj.org/problem?id=1840

题解：http://blog.csdn.net/lyy289065406/article/details/6647387 小优姐讲的很好了

#include<cstdio>
 #include<string>
 #include<iostream>
 #include<cstring>
 #include<map>
 using namespace std;
 
 short hash[25000001];
 int main()
 {
     int a1,a2,a3,a4,a5;
     int x1,x2,x3,x4,x5;
      int sum,ans=0;
        cin>>a1>>a2>>a3>>a4>>a5;
         memset(hash,0,sizeof(hash));
         for(x1=-50; x1<=50; x1++)
         {
             if(!x1) continue;
             for(x2=-50; x2<=50; x2++)
             {
                 if(!x2) continue;
                 sum=a1*x1*x1*x1+a2*x2*x2*x2;
                 if(sum<0)
                 sum+=25000000;
                 hash[sum]++;
             }
         }
         for(x3=-50; x3<=50; x3++)
         {
             if(!x3)  continue;
             for(x4=-50; x4<=50; x4++)
             {
                 if(!x4)  continue;
                 for(x5=-50; x5<=50; x5++)
                 {
                     if(!x5)  continue;
                     sum=a3*x3*x3*x3+a4*x4*x4*x4+a5*x5*x5*x5;
                     if(sum<0)
                     sum+=25000000;
                     ans+=hash[sum];
                 }
             }
         }
         cout<<ans<<endl;
 
     return 0;
 }