hdu1496 Equations Hash

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.

题意：有如上一个公式，给你a,b,c,d，计算满足上式的x1,x2,x3,x4的解的个数。

题解:运用Hash表解决是个非常方便的解法，将式子变形就可得:a*x1^2+b*x2^2=-(c*x3^2+d*x4^2) 。 讲a和b的各种计算结果保存在hash表里面，然后累加hash表里面有多少  -(c*x3^2+d*x4^2)值不为0的，累加即可。

#include
#include
#include
#include
#include
#define maxn 2000003
using namespace std;
int hash[maxn];
int map[110];
int main()
{
    int a,b,c,d;
    for(int i=1;i<101;i++)
        map[i]=i*i;
    while(cin>>a>>b>>c>>d)
    {
        if((a>0&&b>0&&c>0&&d>0)||(b<0&&a<0&&c<0&&d<0))
        {
            cout<<"0"<