poj1182 典型哈希

Eqs

Time Limit: 5000MS Memory Limit: 65536KTotal Submissions: 9907 Accepted: 4840

Description

Consider equations having the following form: 
a1x1³+ a2x2³+ a3x3³+ a4x4³+ a5x5³=0 
The coefficients are given integers from the interval [-50,50]. 
It is consider a solution a system (x1, x2, x3, x4, x5) that verifies the equation, xi∈[-50,50], xi != 0, any i∈{1,2,3,4,5}. 

Determine how many solutions satisfy the given equation. 

Input

The only line of input contains the 5 coefficients a1, a2, a3, a4, a5, separated by blanks.

Output

The output will contain on the first line the number of the solutions for the given equation.

Sample Input

37 29 41 43 47

Sample Output

654

Source

Romania OI 2002

#include <iostream>#include <stdio.h>#include<math.h>using namespace std;#define Max 20000000short hashs[Max*2];int main(){int a1,a2,a3,a4,a5;int i,j,k,l,m,n;long long counts=0;cin>>a1>>a2>>a3>>a4>>a5;for(i=-50;i<=50;i++)for(j=-50;j<=50;j++)for(k=-50;k<=50;k++){if(i!=0&&j!=0&&k!=0){hashs[a1*i*i*i+a2*j*j*j+a3*k*k*k+20000000]++;}}for(i=-50;i<=50;i++)for(j=-50;j<=50;j++){if(i!=0&&j!=0){counts+=hashs[20000000-a4*i*i*i-a5*j*j*j];}}cout<<counts<<endl;}

注意short int在32位C++中只占2字节，比较省空间，本题若使用int类型数组，memory limit会超！