Equations（hdu 1496 二分查找+各种剪枝）

Equations

Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 6927    Accepted Submission(s): 2810

Problem Description

Consider equations having the following form:

a*x1^2+b*x2^2+c*x3^2+d*x4^2=0
a, b, c, d are integers from the interval [-50,50] and any of them cannot be 0.

It is consider a solution a system ( x1,x2,x3,x4 ) that verifies the equation, xi is an integer from [-100,100] and xi != 0, any i ∈{1,2,3,4}.

Determine how many solutions satisfy the given equation.

 

Input

The input consists of several test cases. Each test case consists of a single line containing the 4 coefficients a, b, c, d, separated by one or more blanks.
End of file.

 

Output

For each test case, output a single line containing the number of the solutions.

 

Sample Input

1 2 3 -4

1 1 1 1

 

Sample Output

39088

0

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <iostream>
 #include <cmath>
 using namespace std;
 int a,b,c,d;
 int s[];
 int search(int mid,int k)
 {
     return c*s[k]+d*s[mid];
 }
 void init()
 {
     for(int i=;i<=;i++)    s[i]=i*i;
 }
 int main()
 {
     int i,j,k,ans,y;
     freopen("in.txt","r",stdin);
     init();
     while(cin>>a>>b>>c>>d)
     {
         ans=;
         if(a>&&b>&&c>&&d>||a<&&b<&&c<&&d<){
             printf("0\n");
             continue;
         }
         for(i=;i<=;i++)
         {
             for(j=;j<=;j++)
             {
                 int sum=a*s[i]+b*s[j];
                 if(sum>&&c>&&d>||sum<&&c<&&d<)    continue;
                 for(k=;k<=;k++)
                 {
                     int p=-sum-c*s[k];
                     if(p%d==)
                     {
                         p=p/d;
                         if(binary_search(s+,s+,p))    ans++;
                     }
                 }
             }
         }
         cout<<ans*<<endl;
     }
 }