HDU 1496 Equations (HASH)

Equations

Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3853    Accepted Submission(s): 1551

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

 

Source

“2006校园文化活动月”之“校庆杯”大学生程序设计竞赛暨杭州电子科技大学第四届大学生程序设计竞赛

 

Recommend

LL

 

 

#include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;

const int N=2000010;

int hash[N];

int main(){

    //freopen("input.txt","r",stdin);

    int a,b,c,d;
    while(~scanf("%d%d%d%d",&a,&b,&c,&d)){
        if((a>0 && b>0 && c>0 && d>0) || (a<0 && b<0 && c<0 && d<0)){
            printf("0\n");
            continue;
        }
        memset(hash,0,sizeof(hash));
        for(int i=1;i<=100;i++)
            for(int j=1;j<=100;j++)
                hash[a*i*i+b*j*j+1000000]++;
        int ans=0;
        for(int i=1;i<=100;i++)
            for(int j=1;j<=100;j++)
                ans+=hash[1000000-(c*i*i+d*j*j)];
        printf("%d\n",ans*16);   //每个解有正有负，结果有2^4种 
    }
    return 0;
}