HDOJ1496Equations【hash】

Equations

Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 6564    Accepted Submission(s): 2642

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

 

Author

LL

 

 

#include
#include
#include
using namespace std;
const int MAX=1000010;
int hash1[MAX];
int hash2[MAX];
int main()
{
	int a,b,c,d,i,j,n,m;
	while(scanf("%d%d%d%d",&a,&b,&c,&d)!=EOF){
		if((a<0&&b<0&&c<0&&d<0)||(a>0&&b>0&&c>0&&d>0)){
			printf("%d\n",0);
			continue;
		}
		memset(hash1,0,sizeof(hash1));
		memset(hash2,0,sizeof(hash2));
		for(i=-100;i<=100;++i){
			for(j=-100;j<=100;++j){
				if(i==0||j==0)continue;
				int value=a*i*i+b*j*j;
				if(value>=0){
					hash1[value]++;
				}
				else {
					hash2[-value]++;
				}
			}
		}
		int ans=0;
		for(i=-100;i<=100;++i){
			for(j=-100;j<=100;++j){
				if(i==0||j==0)continue;
				int value=c*i*i+d*j*j;
				if(value>0){
					ans+=hash2[value];
				}
				else {
					ans+=hash1[-value];
				}
			}
		}
		printf("%d\n",ans);
	}
	return 0;
}